day25: complete solution sill need to finish day 21 for the last star!

I think the issue is not testing both possible paths for direction keypads, but doing this naively blows up the compute complexity (and I got the wrong answer)

.github/workflows/test.yaml

@@ -0,0 +1,62 @@
+name: test
+
+on:
+  push:
+    branches: [ main ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  tests:
+    name: AoC 2024
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: setup toolchain
+      uses: actions-rust-lang/setup-rust-toolchain@v1
+      with:
+        cache: true
+        components: clippy, rustfmt
+        toolchain: stable
+        rustflags: ""
+
+    - name: install cargo-aoc
+      run: cargo install --locked cargo-aoc
+
+    - name: get date
+      id: date
+      run: |
+        echo date=$(date +%Y%m%d) > $GITHUB_OUTPUT
+
+    - name: Get cached inputs
+      id: inputs
+      uses: actions/cache@v4
+      with:
+        path: input
+        key: ${{ steps.date.outputs.date }}
+
+    - name: Get inputs from source
+      if: steps.inputs.outputs.cache-hit != 'true'
+      run: |
+        cargo aoc credentials ${{ secrets.AOC_SESSION }}
+        for i in $(seq 1 25); do
+          dayfmt=$(printf %02d $i)
+          if [ ${{ steps.date.outputs.date }} -ge 202412${dayfmt} ]; then
+            cargo aoc input --year 2024 --day $i
+          fi
+        done
+
+    - name: cargo test
+      run: cargo test --lib
+
+    - name: rustfmt
+      run: cargo fmt --all -- --check
+
+    - name: clippy
+      run: cargo clippy --lib --tests -- -D warnings
+      if: always()
+
+    - name: full run
+      run: cargo run --release
+      if: always()

.gitignore

@@ -1,4 +1,7 @@
 **/target
 input
 flamegraph.svg
-perf.data
+perf.data*
+guesses
+.aoc_tiles/*
+!.aoc_tiles/tiles/

.pre-commit-config.yaml

@@ -0,0 +1,30 @@
+repos:
+  - repo: local
+    hooks:
+      - id: rust-linting
+        name: Rust linting
+        entry: cargo fmt --all --
+        pass_filenames: true
+        types: [file, rust]
+        language: system
+      - id: rust-clippy
+        name: Rust clippy
+        entry: cargo clippy --lib --all-features --tests -- -D warnings
+        pass_filenames: false
+        types: [file, rust]
+        language: system
+  - repo: https://github.com/LiquidFun/aoc_tiles
+    rev: 0.6.2
+    hooks:
+      - id: aoc-tiles
+        # Optionally use these arguments. Auto add tiles to git adds the tiles to git,
+        # possibly amends your commit by creating the tile images and updating the README.
+        # Language sorting shows the preference of the order of the languages to use.
+        # Exclude paterns are globs which can be used to exclude files when creating
+        # the tiles. See the customization section in the README for more flags.
+        # Simply remove the comments (#) below for args and the flags you want.
+        args:
+          - --auto-add-tiles-to-git=amend
+          - --overwrite-year=2024
+        #     - --language-sorting=jl,kt,py,rs
+        #     - --exclude-patterns=2021/*/*.apl,2021/*/*.py,2021/*/*.cpp

1/src/main.rs

@@ -1,105 +0,0 @@
-use std::collections::HashMap;
-use std::fs::File;
-use std::io::{BufRead, BufReader, Lines};
-use std::iter::zip;
-use std::time::Instant;
-
-// BOILERPLATE
-type InputIter = Lines<BufReader<File>>;
-
-fn get_input() -> InputIter {
-    let f = File::open("input").unwrap();
-    let br = BufReader::new(f);
-    br.lines()
-}
-
-fn main() {
-    let start = Instant::now();
-    let ans1 = problem1(get_input());
-    let duration = start.elapsed();
-    println!("Problem 1 solution: {} [{}s]", ans1, duration.as_secs_f64());
-
-    let start = Instant::now();
-    let ans2 = problem2(get_input());
-    let duration = start.elapsed();
-    println!("Problem 2 solution: {} [{}s]", ans2, duration.as_secs_f64());
-}
-
-struct Locations {
-    left: Vec<u64>,
-    right: Vec<u64>,
-}
-
-impl<T: BufRead> From<Lines<T>> for Locations {
-    fn from(input: Lines<T>) -> Self {
-        let mut left = Vec::new();
-        let mut right = Vec::new();
-        for line in input.map(|i| i.unwrap()) {
-            let parts: Vec<&str> = line.split_ascii_whitespace().collect();
-            left.push(parts[0].parse::<u64>().unwrap());
-            right.push(parts[1].parse::<u64>().unwrap());
-        }
-        Self { left, right }
-    }
-}
-
-impl Locations {
-    fn sort(&mut self) {
-        self.left.sort();
-        self.right.sort();
-    }
-    fn right_count(&self) -> HashMap<u64, u64> {
-        let mut right_count: HashMap<u64, u64> = HashMap::new();
-        for rval in &self.right {
-            right_count.insert(*rval, *right_count.get(rval).unwrap_or(&0) + 1);
-        }
-        right_count
-    }
-}
-
-// PROBLEM 1 solution
-
-fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
-    let mut locations = Locations::from(input);
-    locations.sort();
-
-    zip(locations.left, locations.right)
-        .map(|(l, r)| u64::abs_diff(l, r))
-        .sum()
-}
-
-// PROBLEM 2 solution
-fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
-    let locations = Locations::from(input);
-    let right_count = locations.right_count();
-    locations
-        .left
-        .iter()
-        .map(|l| l * right_count.get(l).unwrap_or(&0))
-        .sum::<u64>()
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::*;
-    use std::io::Cursor;
-
-    const EXAMPLE: &str = &"3   4
-4   3
-2   5
-1   3
-3   9
-3   3";
-
-    #[test]
-    fn problem1_example() {
-        let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem1(c.lines()), 11);
-    }
-
-    #[test]
-    fn problem2_example() {
-        let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem2(c.lines()), 31);
-    }
-}

2/Cargo.lock

@@ -1,7 +0,0 @@
-# This file is automatically @generated by Cargo.
-# It is not intended for manual editing.
-version = 3
-
-[[package]]
-name = "day2"
-version = "0.1.0"

2/src/main.rs

@@ -1,133 +0,0 @@
-use std::fs::File;
-use std::io::{BufRead, BufReader, Lines};
-use std::time::{Duration, Instant};
-
-// BOILERPLATE
-type InputIter = Lines<BufReader<File>>;
-
-fn get_input() -> InputIter {
-    let f = File::open("input").unwrap();
-    let br = BufReader::new(f);
-    br.lines()
-}
-
-fn duration_format(duration: Duration) -> String {
-    match duration.as_secs_f64() {
-        x if x > 1.0 => format!("{:.3}s", x),
-        x if x > 0.010 => format!("{:.3}ms", x * 1e3),
-        x => format!("{:.3}us", x * 1e6),
-    }
-}
-
-fn main() {
-    let input = get_input();
-    let start = Instant::now();
-    let ans1 = problem1(input);
-    let duration1 = start.elapsed();
-    println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
-
-    let input = get_input();
-    let start = Instant::now();
-    let ans2 = problem2(input);
-    let duration2 = start.elapsed();
-    println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
-    println!("Total duration: {}", duration_format(duration1 + duration2));
-}
-
-struct Reports {
-    reports: Vec<Vec<u64>>,
-}
-
-impl<T: BufRead> From<Lines<T>> for Reports {
-    fn from(lines: Lines<T>) -> Self {
-        let mut reports = Vec::new();
-        for line in lines.map(|i| i.unwrap()) {
-            reports.push(
-                line.split_ascii_whitespace()
-                    .map(|record| record.parse::<u64>().unwrap())
-                    .collect(),
-            )
-        }
-        Reports { reports }
-    }
-}
-
-impl Reports {
-    fn is_safe(report: &Vec<u64>) -> bool {
-        let mut ascending: bool = true;
-        let mut descending: bool = true;
-        for (a, b) in report.iter().zip(report.iter().skip(1)) {
-            if a > b {
-                ascending = false
-            }
-            if a < b {
-                descending = false;
-            }
-            let ad = a.abs_diff(*b);
-            if !(ad >= 1 && ad <= 3) || (!ascending && !descending) {
-                return false;
-            };
-        }
-        return true;
-    }
-    fn count_safe(&self) -> u64 {
-        self.reports.iter().filter(|report| Self::is_safe(report)).count() as u64
-    }
-    fn is_dumb_dampened_safe(report: &Vec<u64>) -> bool {
-        if Self::is_safe(report) {
-            return true;
-        }
-        for i in 0..report.len() {
-            let mut new_vec = report.clone();
-            new_vec.remove(i);
-            if Self::is_safe(&new_vec) {
-                return true;
-            }
-        }
-        false
-    }
-    fn dampened_count_safe(&self) -> u64 {
-        self.reports
-            .iter()
-            .filter(|report| Self::is_dumb_dampened_safe(report))
-            .count() as u64
-    }
-}
-
-// PROBLEM 1 solution
-
-fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
-    let reports = Reports::from(input);
-    reports.count_safe()
-}
-
-// PROBLEM 2 solution
-fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
-    let reports = Reports::from(input);
-    reports.dampened_count_safe()
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::*;
-    use std::io::Cursor;
-
-    const EXAMPLE: &str = &"7 6 4 2 1
-1 2 7 8 9
-9 7 6 2 1
-1 3 2 4 5
-8 6 4 4 1
-1 3 6 7 9";
-
-    #[test]
-    fn problem1_example() {
-        let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem1(c.lines()), 2);
-    }
-
-    #[test]
-    fn problem2_example() {
-        let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem2(c.lines()), 4);
-    }
-}

3/Cargo.lock

@@ -1,71 +0,0 @@
-# This file is automatically @generated by Cargo.
-# It is not intended for manual editing.
-version = 3
-
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-version = "1.1.3"
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- "memchr",
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3/Cargo.toml

@@ -1,8 +0,0 @@
-[package]
-name = "day3"
-version = "0.1.0"
-edition = "2021"
-
-[dependencies]
-nom = "7.1.3"
-regex = { version = "1.11.1", default-features = false, features = ["perf", "std"] }

3/src/main.rs

@@ -1,90 +0,0 @@
-use regex::bytes::Regex;
-use std::fs::File;
-use std::io::{BufRead, BufReader, Lines};
-use std::time::{Duration, Instant};
-
-// BOILERPLATE
-type InputIter = Lines<BufReader<File>>;
-
-pub fn get_input() -> InputIter {
-    let f = File::open("input").unwrap();
-    let br = BufReader::new(f);
-    br.lines()
-}
-
-fn duration_format(duration: Duration) -> String {
-    match duration.as_secs_f64() {
-        x if x > 1.0 => format!("{:.3}s", x),
-        x if x > 0.010 => format!("{:.3}ms", x * 1e3),
-        x => format!("{:.3}us", x * 1e6),
-    }
-}
-
-fn main() {
-    let input = get_input();
-    let start = Instant::now();
-    let ans1 = problem1(input);
-    let duration1 = start.elapsed();
-    println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
-
-    let input = get_input();
-    let start = Instant::now();
-    let ans2 = problem2(input);
-    let duration2 = start.elapsed();
-    println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
-    println!("Total duration: {}", duration_format(duration1 + duration2));
-}
-
-// PROBLEM 1 solution
-
-fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
-    let mut sum = 0u64;
-    let re = Regex::new(r"(?-u)mul\((\d+),(\d+)\)").unwrap();
-    for line in input.map(|i| i.unwrap()) {
-        let line = line.as_bytes();
-        for m in re.captures_iter(line) {
-            sum +=  std::str::from_utf8(&m[1]).unwrap().parse::<u64>().unwrap() * std::str::from_utf8(&m[2]).unwrap().parse::<u64>().unwrap();
-        }
-    }
-    sum
-}
-
-// PROBLEM 2 solution
-fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
-    let mut sum = 0u64;
-    let mut do_mul = true;
-    let re = Regex::new(r"(?-u)(do\(\)|don't\(\)|mul\((\d+),(\d+)\))").unwrap();
-    for line in input.map(|i| i.unwrap()) {
-        let line = line.as_bytes();
-        for m in re.captures_iter(line) {
-            match std::str::from_utf8(&m[1]).unwrap() {
-                "do()" => do_mul = true,
-                "don't()" => do_mul = false,
-                _ if do_mul => sum += std::str::from_utf8(&m[2]).unwrap().parse::<u64>().unwrap() * std::str::from_utf8(&m[3]).unwrap().parse::<u64>().unwrap(),
-                _ => {}
-            }
-        }
-    }
-    sum
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::*;
-    use std::io::Cursor;
-
-    const EXAMPLE1: &str = &"xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
-    const EXAMPLE2: &str = &"xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
-
-    #[test]
-    fn problem1_example() {
-        let c = Cursor::new(EXAMPLE1);
-        assert_eq!(problem1(c.lines()), 161);
-    }
-
-    #[test]
-    fn problem2_example() {
-        let c = Cursor::new(EXAMPLE2);
-        assert_eq!(problem2(c.lines()), 48);
-    }
-}

4/Cargo.lock

@@ -1,7 +0,0 @@
-# This file is automatically @generated by Cargo.
-# It is not intended for manual editing.
-version = 3
-
-[[package]]
-name = "day4"
-version = "0.1.0"

4/Cargo.toml

@@ -1,6 +0,0 @@
-[package]
-name = "day4"
-version = "0.1.0"
-edition = "2021"
-
-[dependencies]

Cargo.lock

@@ -0,0 +1,666 @@
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+# It is not intended for manual editing.
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+
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+ "zerocopy",
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README.md

@@ -0,0 +1,80 @@
+<!-- AOC TILES BEGIN -->
+<h1 align="center">
+  2024 - 48 ⭐ - Rust
+</h1>
+<a href="src/day1.rs">
+  <img src=".aoc_tiles/tiles/2024/01.png" width="161px">
+</a>
+<a href="src/day2.rs">
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+<a href="src/day3.rs">
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+</a>
+<a href="src/day4.rs">
+  <img src=".aoc_tiles/tiles/2024/04.png" width="161px">
+</a>
+<a href="src/day5.rs">
+  <img src=".aoc_tiles/tiles/2024/05.png" width="161px">
+</a>
+<a href="src/day6.rs">
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+</a>
+<a href="src/day7.rs">
+  <img src=".aoc_tiles/tiles/2024/07.png" width="161px">
+</a>
+<a href="src/day8.rs">
+  <img src=".aoc_tiles/tiles/2024/08.png" width="161px">
+</a>
+<a href="src/day9.rs">
+  <img src=".aoc_tiles/tiles/2024/09.png" width="161px">
+</a>
+<a href="src/day10.rs">
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+</a>
+<a href="src/day11.rs">
+  <img src=".aoc_tiles/tiles/2024/11.png" width="161px">
+</a>
+<a href="src/day12.rs">
+  <img src=".aoc_tiles/tiles/2024/12.png" width="161px">
+</a>
+<a href="src/day13.rs">
+  <img src=".aoc_tiles/tiles/2024/13.png" width="161px">
+</a>
+<a href="src/day14.rs">
+  <img src=".aoc_tiles/tiles/2024/14.png" width="161px">
+</a>
+<a href="src/day15.rs">
+  <img src=".aoc_tiles/tiles/2024/15.png" width="161px">
+</a>
+<a href="src/day16.rs">
+  <img src=".aoc_tiles/tiles/2024/16.png" width="161px">
+</a>
+<a href="src/day17.rs">
+  <img src=".aoc_tiles/tiles/2024/17.png" width="161px">
+</a>
+<a href="src/day18.rs">
+  <img src=".aoc_tiles/tiles/2024/18.png" width="161px">
+</a>
+<a href="src/day19.rs">
+  <img src=".aoc_tiles/tiles/2024/19.png" width="161px">
+</a>
+<a href="src/day20.rs">
+  <img src=".aoc_tiles/tiles/2024/20.png" width="161px">
+</a>
+<a href="src/day21.rs">
+  <img src=".aoc_tiles/tiles/2024/21.png" width="161px">
+</a>
+<a href="src/day22.rs">
+  <img src=".aoc_tiles/tiles/2024/22.png" width="161px">
+</a>
+<a href="src/day23.rs">
+  <img src=".aoc_tiles/tiles/2024/23.png" width="161px">
+</a>
+<a href="src/day24.rs">
+  <img src=".aoc_tiles/tiles/2024/24.png" width="161px">
+</a>
+<a href="src/day25.rs">
+  <img src=".aoc_tiles/tiles/2024/25.png" width="161px">
+</a>
+<!-- AOC TILES END -->

src/day1.rs

@@ -0,0 +1,92 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use rustc_hash::FxHashMap;
+use std::io::{BufRead, Lines};
+
+type HashMap<K, V> = FxHashMap<K, V>;
+
+#[aoc_generator(day1)]
+pub fn get_input(input: &[u8]) -> Locations {
+    Locations::from(input.lines())
+}
+
+#[derive(Clone)]
+pub struct Locations {
+    left: Vec<u64>,
+    right: Vec<u64>,
+}
+
+impl<T: BufRead> From<Lines<T>> for Locations {
+    fn from(input: Lines<T>) -> Self {
+        let mut left = Vec::new();
+        let mut right = Vec::new();
+        for line in input.map(|i| i.unwrap()) {
+            let parts: Vec<&str> = line.split_ascii_whitespace().collect();
+            left.push(parts[0].parse::<u64>().unwrap());
+            right.push(parts[1].parse::<u64>().unwrap());
+        }
+        Self { left, right }
+    }
+}
+
+impl Locations {
+    fn sort(&mut self) {
+        self.left.sort();
+        self.right.sort();
+    }
+    fn right_count(&self) -> HashMap<u64, u64> {
+        let mut right_count: HashMap<u64, u64> = HashMap::default();
+        for rval in &self.right {
+            right_count.insert(*rval, *right_count.get(rval).unwrap_or(&0) + 1);
+        }
+        right_count
+    }
+}
+
+// PROBLEM 1 solution
+#[aoc(day1, part1)]
+pub fn part1(locations: &Locations) -> u64 {
+    let mut locations = locations.clone();
+    locations.sort();
+
+    locations
+        .left
+        .iter()
+        .zip(locations.right)
+        .map(|(l, r)| u64::abs_diff(*l, r))
+        .sum()
+}
+
+// PROBLEM 2 solution
+#[aoc(day1, part2)]
+pub fn part2(locations: &Locations) -> u64 {
+    let right_count = locations.right_count();
+    locations
+        .left
+        .iter()
+        .map(|l| l * right_count.get(l).unwrap_or(&0))
+        .sum::<u64>()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day1::*;
+
+    const EXAMPLE: &[u8] = b"3   4
+4   3
+2   5
+1   3
+3   9
+3   3";
+
+    #[test]
+    fn part1_example() {
+        let input = get_input(EXAMPLE);
+        assert_eq!(part1(&input), 11);
+    }
+
+    #[test]
+    fn part2_example() {
+        let input = get_input(EXAMPLE);
+        assert_eq!(part2(&input), 31);
+    }
+}

src/day10.rs

@@ -0,0 +1,111 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use grid::Grid;
+use itertools::Itertools;
+use std::io::BufRead;
+
+#[aoc_generator(day10)]
+pub fn get_input(input: &[u8]) -> TrailMap {
+    TrailMap::from(input)
+}
+
+pub struct TrailMap {
+    map: Grid<u8>,
+}
+
+impl<T: BufRead> From<T> for TrailMap {
+    fn from(input: T) -> Self {
+        Self { map: input.into() }
+    }
+}
+
+impl TrailMap {
+    fn trailheads(&self) -> Vec<(i64, i64)> {
+        self.map
+            .data
+            .iter()
+            .enumerate()
+            .filter(|(_, v)| **v == b'0')
+            .map(|(i, _v)| self.map.coord(i as i64).unwrap().into())
+            .collect_vec()
+    }
+    fn count_reachable_from(&self, pos: &(i64, i64), needle: u8, visited: &mut Grid<bool>) -> u64 {
+        if visited.get(pos) == Some(&true) {
+            return 0;
+        } else {
+            visited.set(pos, true);
+        }
+        let our_val = self.map.get(pos).unwrap();
+        if *our_val == needle {
+            return 1;
+        }
+        // adjacents that are +1
+        [(-1, 0), (1, 0), (0, -1), (0, 1)] // left, right, up, down
+            .iter()
+            .map(|(x_ofs, y_ofs)| (pos.0 + x_ofs, pos.1 + y_ofs)) // get target position
+            .map(|target_pos| (target_pos, self.map.get(&target_pos))) // get value at that position
+            .filter(|(_, val)| *val == Some(&(our_val + 1))) // only interested if it's our value + 1
+            .map(|(pos, _)| pos) // discard the value
+            .map(|pos| self.count_reachable_from(&pos, needle, visited))
+            .sum()
+    }
+
+    fn count_paths_to(&self, pos: &(i64, i64), needle: u8) -> u64 {
+        let our_val = self.map.get(pos).unwrap();
+        if *our_val == needle {
+            return 1;
+        }
+        [(-1, 0), (1, 0), (0, -1), (0, 1)] // left, right, up, down
+            .iter()
+            .map(|(x_ofs, y_ofs)| (pos.0 + x_ofs, pos.1 + y_ofs)) // get target position
+            .map(|target_pos| (target_pos, self.map.get(&target_pos))) // get value at that position
+            .filter(|(_, val)| *val == Some(&(our_val + 1))) // only interested if it's our value + 1
+            .map(|(pos, _)| pos) // discard the value
+            .map(|mov| self.count_paths_to(&mov, needle))
+            .sum::<u64>()
+    }
+}
+
+// PROBLEM 1 solution
+#[aoc(day10, part1)]
+pub fn part1(map: &TrailMap) -> u64 {
+    map.trailheads()
+        .iter()
+        .map(|pos| {
+            let mut visited = Grid::with_shape(map.map.width(), map.map.height(), false);
+            map.count_reachable_from(pos, b'9', &mut visited)
+        })
+        .sum()
+}
+
+// PROBLEM 2 solution
+#[aoc(day10, part2)]
+pub fn part2(map: &TrailMap) -> u64 {
+    map.trailheads()
+        .iter()
+        .map(|pos| map.count_paths_to(pos, b'9'))
+        .sum::<u64>()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day10::*;
+
+    const EXAMPLE: &[u8] = b"89010123
+78121874
+87430965
+96549874
+45678903
+32019012
+01329801
+10456732";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 36);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 81);
+    }
+}

src/day11.rs

@@ -0,0 +1,103 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use rustc_hash::FxHashMap;
+use std::iter::repeat;
+
+type IntType = u64;
+type CacheType = FxHashMap<Stone, IntType>;
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+struct Stone(IntType);
+struct Stones(Vec<Stone>);
+
+enum BlinkResult {
+    One(Stone),
+    Two(Stone, Stone),
+}
+
+impl From<&str> for Stones {
+    fn from(input: &str) -> Self {
+        Stones(
+            input
+                .split_ascii_whitespace()
+                .map(|v| Stone(v.parse().unwrap()))
+                .collect_vec(),
+        )
+    }
+}
+
+fn parse(input: &str) -> Stones {
+    Stones::from(input)
+}
+
+impl Stone {
+    fn blink_once(&self) -> BlinkResult {
+        let n_digits = if self.0 == 0 { 1 } else { self.0.ilog10() + 1 };
+        if self.0 == 0 {
+            BlinkResult::One(Stone(1))
+        } else if n_digits % 2 == 0 {
+            let split_factor = (10 as IntType).pow(n_digits / 2);
+            let parts = (self.0 / split_factor, self.0 % split_factor);
+            BlinkResult::Two(Stone(parts.0), Stone(parts.1))
+        } else {
+            BlinkResult::One(Stone(&self.0 * 2024))
+        }
+    }
+}
+
+fn count_blinks(stone: &Stone, blink: usize, cache: &mut Vec<CacheType>) -> IntType {
+    if cache[blink].contains_key(stone) {
+        return cache[blink][stone];
+    }
+    let stones = stone.blink_once();
+    let result = if blink == 0 {
+        match stones {
+            BlinkResult::One(_) => 1,
+            BlinkResult::Two(_, _) => 2,
+        }
+    } else {
+        match stones {
+            BlinkResult::One(s) => count_blinks(&s, blink - 1, cache),
+            BlinkResult::Two(s1, s2) => count_blinks(&s1, blink - 1, cache) + count_blinks(&s2, blink - 1, cache),
+        }
+    };
+    cache[blink].insert(stone.clone(), result);
+    cache[blink][stone]
+}
+
+fn blink_stones(stones: Stones, blinks: usize) -> IntType {
+    let mut cache = Vec::from_iter(repeat(CacheType::default()).take(blinks));
+    stones
+        .0
+        .iter()
+        .map(|stone| count_blinks(stone, blinks - 1, &mut cache))
+        .sum()
+}
+
+#[aoc(day11, part1)]
+pub fn part1(input: &str) -> IntType {
+    let stones = parse(input);
+    blink_stones(stones, 25)
+}
+
+#[aoc(day11, part2)]
+pub fn part2(input: &str) -> IntType {
+    let stones = parse(input);
+    blink_stones(stones, 75)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    pub const EXAMPLE: &str = "125 17";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 55312);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE), 65601038650482);
+    }
+}

src/day12.rs

@@ -0,0 +1,176 @@
+use std::str::FromStr;
+
+use aoc_runner_derive::aoc;
+use grid::{Coord2d, Grid};
+
+pub struct Farm {
+    map: Grid<u8>,
+}
+
+impl FromStr for Farm {
+    type Err = <Grid<u8> as FromStr>::Err;
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        Ok(Self { map: input.parse()? })
+    }
+}
+
+impl Farm {
+    fn compute_region(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) {
+        let our_plant = self.map.get(pos).unwrap();
+
+        visited.set(pos, true);
+
+        [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)]
+            .map(|ofs| pos + ofs)
+            .iter()
+            .fold((1, 0), |(area, perimeter), adj| {
+                match self.map.get(adj) {
+                    Some(plant) if plant == our_plant => {
+                        if visited.get(adj) == Some(&false) {
+                            // add the perimeter of the growth from there if not visited yet
+                            let (add_area, add_perimeter) = self.compute_region(adj, visited);
+                            (area + add_area, perimeter + add_perimeter)
+                        } else {
+                            (area, perimeter)
+                        }
+                    }
+                    Some(_) | None => (area, perimeter + 1),
+                }
+            })
+    }
+
+    fn regions_cost(&self) -> u64 {
+        let mut visited = Grid::with_shape(self.map.width(), self.map.height(), false);
+        let mut cost = 0;
+        for y in 0..self.map.height() {
+            for x in 0..self.map.width() {
+                cost += match visited.get(&(x, y)) {
+                    Some(false) => {
+                        let (area, perim) = self.compute_region(
+                            &Coord2d {
+                                x: x as i64,
+                                y: y as i64,
+                            },
+                            &mut visited,
+                        );
+                        area * perim
+                    }
+                    Some(_) | None => 0,
+                }
+            }
+        }
+        cost
+    }
+    fn count_corners(&self, pos: &Coord2d) -> u64 {
+        // NOTE: Iterating twice is faster than combining conditions in one pass
+        // BAB
+        // AAA has 4 inside corners (pos at centre). check that for AA A's exist and B doesn't for each rotation
+        // BAB                                                      AB
+        let our_plant = self.map.get(pos);
+        let inside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)]
+            .iter()
+            .filter(|inside_corner| {
+                self.map.get(&(pos + **inside_corner)) != our_plant
+                    && self.map.get(&(pos + (inside_corner.0, 0))) == our_plant
+                    && self.map.get(&(pos + (0, inside_corner.1))) == our_plant
+            })
+            .count();
+        // BBB
+        // BAB has 4 outside corners (pos at centre). check that for AB the  B are both not equal to A for each rot
+        // BBB                                                       BB     B
+        let outside_corners = [(1i64, 1i64), (-1, 1), (1, -1), (-1, -1)]
+            .iter()
+            .filter(|outside_corner| {
+                self.map.get(&(pos + (outside_corner.0, 0))) != our_plant
+                    && self.map.get(&(pos + (0, outside_corner.1))) != our_plant
+            })
+            .count();
+        (inside_corners + outside_corners) as u64
+    }
+    fn region_corners(&self, pos: &Coord2d, visited: &mut Grid<bool>) -> (u64, u64) {
+        let our_plant = self.map.get(pos).unwrap();
+
+        visited.set(pos, true);
+
+        [(-1i64, 0i64), (1, 0), (0, -1), (0, 1)]
+            .map(|ofs| pos + ofs)
+            .iter()
+            .fold((1, self.count_corners(pos)), |(area, corners), adj| {
+                match self.map.get(adj) {
+                    Some(plant) if plant == our_plant => {
+                        if visited.get(adj) == Some(&false) {
+                            // add the perimeter of the growth from there if not visited yet
+                            let (n_area, n_corners) = self.region_corners(adj, visited);
+                            (area + n_area, corners + n_corners)
+                        } else {
+                            (area, corners)
+                        }
+                    }
+                    Some(_) | None => (area, corners),
+                }
+            })
+    }
+    fn regions_discount_cost(&self) -> u64 {
+        let mut visited = self.map.same_shape(false);
+        let mut cost = 0;
+        for y in 0..self.map.height() {
+            for x in 0..self.map.width() {
+                cost += match visited.get(&(x, y)) {
+                    Some(false) => {
+                        let (area, corners) = self.region_corners(
+                            &Coord2d {
+                                x: x as i64,
+                                y: y as i64,
+                            },
+                            &mut visited,
+                        );
+                        area * corners
+                    }
+                    Some(_) | None => 0,
+                }
+            }
+        }
+        cost
+    }
+}
+
+fn parse(input: &str) -> Farm {
+    input.parse().unwrap()
+}
+
+#[aoc(day12, part1)]
+pub fn part1(input: &str) -> u64 {
+    let farm = parse(input);
+    farm.regions_cost()
+}
+
+#[aoc(day12, part2)]
+pub fn part2(input: &str) -> u64 {
+    let farm = parse(input);
+    farm.regions_discount_cost()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "RRRRIICCFF
+RRRRIICCCF
+VVRRRCCFFF
+VVRCCCJFFF
+VVVVCJJCFE
+VVIVCCJJEE
+VVIIICJJEE
+MIIIIIJJEE
+MIIISIJEEE
+MMMISSJEEE";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 1930);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE), 1206);
+    }
+}

src/day13.rs

@@ -0,0 +1,135 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use regex::Regex;
+use std::str::Lines;
+
+#[derive(Debug, Clone)]
+pub struct MachineAction(i64, i64);
+
+#[derive(Debug, Clone)]
+struct ClawMachine {
+    button_a: MachineAction,
+    button_b: MachineAction,
+    prize: (i64, i64),
+}
+
+impl ClawMachine {
+    fn consume_from_input(input: &mut Lines) -> Option<Self> {
+        // consume any empty lines at the front
+        let ofs_re = Regex::new(r"X([+-]\d+), Y([+-]\d+)").unwrap();
+        let prize_re = Regex::new(r"X=(\d+), Y=(\d+)").unwrap();
+        // consume 3 lines - a, b, prize
+        if let Some((a_line, b_line, prize_line)) = input.filter(|l| !l.is_empty()).take(3).collect_tuple() {
+            let a_caps = ofs_re.captures(a_line).unwrap();
+            let b_caps = ofs_re.captures(b_line).unwrap();
+            let prize_caps = prize_re.captures(prize_line).unwrap();
+            let button_a = MachineAction(
+                a_caps.get(1).unwrap().as_str().parse().unwrap(),
+                a_caps.get(2).unwrap().as_str().parse().unwrap(),
+            );
+            let button_b = MachineAction(
+                b_caps.get(1).unwrap().as_str().parse().unwrap(),
+                b_caps.get(2).unwrap().as_str().parse().unwrap(),
+            );
+            let prize = (
+                prize_caps.get(1).unwrap().as_str().parse().unwrap(),
+                prize_caps.get(2).unwrap().as_str().parse().unwrap(),
+            );
+            Some(Self {
+                button_a,
+                button_b,
+                prize,
+            })
+        } else {
+            None
+        }
+    }
+    fn cost(moves: (i64, i64)) -> i64 {
+        moves.0 * 3 + moves.1
+    }
+    fn cheapest_prize(&self) -> Option<i64> {
+        let remainder_a = (self.button_b.0 * self.prize.1 - self.button_b.1 * self.prize.0)
+            % (self.button_b.0 * self.button_a.1 - self.button_a.0 * self.button_b.1);
+        let a = (self.button_b.0 * self.prize.1 - self.button_b.1 * self.prize.0)
+            / (self.button_b.0 * self.button_a.1 - self.button_a.0 * self.button_b.1);
+        let remainder_b = (self.prize.0 - (self.button_a.0 * a)) % self.button_b.0;
+        let b = (self.prize.0 - (self.button_a.0 * a)) / self.button_b.0;
+        if remainder_a == 0 && remainder_b == 0 {
+            Some(Self::cost((a, b)))
+        } else {
+            None
+        }
+    }
+    fn offset(&mut self, offset: i64) {
+        self.prize = (self.prize.0 + offset, self.prize.1 + offset)
+    }
+}
+
+#[derive(Debug, Clone)]
+struct ClawMachines {
+    machines: Vec<ClawMachine>,
+}
+
+impl From<&str> for ClawMachines {
+    fn from(input: &str) -> Self {
+        let mut machines = Vec::new();
+        let mut lines = input.lines();
+        while let Some(machine) = ClawMachine::consume_from_input(&mut lines) {
+            machines.push(machine);
+        }
+        Self { machines }
+    }
+}
+
+fn parse(input: &str) -> ClawMachines {
+    ClawMachines::from(input)
+}
+
+#[aoc(day13, part1)]
+fn part1(input: &str) -> i64 {
+    let machines = parse(input);
+    machines.machines.iter().filter_map(|m| m.cheapest_prize()).sum()
+}
+
+#[aoc(day13, part2)]
+fn part2(input: &str) -> i64 {
+    let mut machines = parse(input);
+    machines
+        .machines
+        .iter_mut()
+        .filter_map(|m| {
+            m.offset(10000000000000);
+            m.cheapest_prize()
+        })
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 480);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE), 875318608908);
+    }
+}

src/day14.rs

@@ -0,0 +1,178 @@
+use aoc_runner_derive::aoc;
+use colored::Colorize;
+use grid::{AsCoord2d, Grid};
+use misc::CustomWrapped;
+use nom::{
+    bytes::complete::tag,
+    character::complete::digit1,
+    combinator::{map_res, opt, recognize},
+    sequence::{preceded, separated_pair},
+    IResult,
+};
+use std::{fmt::Display, str::FromStr};
+
+type Coord = (CustomWrapped<i64>, CustomWrapped<i64>);
+struct Robot {
+    pos: Coord,
+    vel: (i64, i64),
+}
+
+struct Robots {
+    robots: Vec<Robot>,
+    width: i64,
+    height: i64,
+}
+
+#[derive(Debug, Eq, PartialEq)]
+enum Quadrant {
+    NW = 0,
+    NE = 1,
+    SW = 2,
+    SE = 3,
+}
+
+fn nom_i64(input: &str) -> IResult<&str, i64> {
+    let (i, number) = map_res(recognize(preceded(opt(tag("-")), digit1)), i64::from_str)(input)?;
+    Ok((i, number))
+}
+fn nom_i64_pair(input: &str) -> IResult<&str, (i64, i64)> {
+    let (i, pair) = separated_pair(nom_i64, tag(","), nom_i64)(input)?;
+    Ok((i, pair))
+}
+
+impl Robot {
+    fn from_str(s: &str, bounds: (i64, i64)) -> Self {
+        let (s, pos) = preceded(tag("p="), nom_i64_pair)(s).unwrap();
+        let (_, vel) = preceded(tag(" v="), nom_i64_pair)(s).unwrap();
+        Self {
+            pos: (CustomWrapped::new(pos.0, bounds.0), CustomWrapped::new(pos.1, bounds.1)),
+            vel,
+        }
+    }
+    fn step(&mut self, count: i64) {
+        self.pos.0 += self.vel.x() * count;
+        self.pos.1 += self.vel.y() * count;
+    }
+    fn quad(&self, bounds: (i64, i64)) -> Option<Quadrant> {
+        let splits = (bounds.0 / 2, bounds.1 / 2);
+        if self.pos.0 < splits.0 && self.pos.1 < splits.1 {
+            Some(Quadrant::NW)
+        } else if self.pos.0 > splits.0 && self.pos.1 < splits.1 {
+            Some(Quadrant::NE)
+        } else if self.pos.0 < splits.0 && self.pos.1 > splits.1 {
+            Some(Quadrant::SW)
+        } else if self.pos.0 > splits.0 && self.pos.1 > splits.1 {
+            Some(Quadrant::SE)
+        } else {
+            None
+        }
+    }
+}
+
+impl Robots {
+    fn from_vec(robots: Vec<Robot>, width: i64, height: i64) -> Self {
+        Self { robots, width, height }
+    }
+    fn as_grid(&self) -> Grid<usize> {
+        let mut grid = Grid::with_shape(self.width as usize, self.height as usize, 0usize);
+        for r in &self.robots {
+            grid.increment(&(r.pos.0.val, r.pos.1.val), 1usize);
+        }
+        grid
+    }
+    fn count_quads(&self) -> [u64; 4] {
+        let mut counts = [0; 4];
+        for r in &self.robots {
+            if let Some(q) = r.quad((self.width, self.height)) {
+                counts[q as usize] += 1
+            }
+        }
+        counts
+    }
+    fn step(&mut self, count: i64) {
+        for robot in &mut self.robots {
+            robot.step(count)
+        }
+    }
+}
+
+impl Display for Robots {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let grid = self.as_grid();
+        for row in 0..grid.height() {
+            for col in 0..grid.width() {
+                if *grid.get(&(col, row)).unwrap() != 0 {
+                    "█".green().fmt(f)?;
+                } else {
+                    " ".color(colored::Color::Black).fmt(f)?;
+                }
+            }
+            writeln!(f)?
+        }
+        Ok(())
+    }
+}
+
+fn parse(input: &str, width: i64, height: i64) -> Vec<Robot> {
+    input.lines().map(|l| Robot::from_str(l, (width, height))).collect()
+}
+
+fn part1_impl(input: &str, width: i64, height: i64) -> u64 {
+    let mut robots = Robots::from_vec(parse(input, width, height), width, height);
+    robots.step(100);
+    let counts = robots.count_quads();
+    counts.iter().product()
+}
+
+#[aoc(day14, part1)]
+pub fn part1(input: &str) -> u64 {
+    part1_impl(input, 101, 103)
+}
+
+#[aoc(day14, part2)]
+pub fn part2(input: &str) -> u64 {
+    let width = 101;
+    let height = 103;
+    let mut robots = Robots::from_vec(parse(input, width, height), width, height);
+    for i in 1.. {
+        robots.step(1);
+        // collect into lines
+        let g = robots.as_grid();
+        if g.data
+            .chunk_by(|a, b| *a != 0 && *b != 0)
+            .filter(|c| !c.is_empty() && c[0] != 0)
+            .any(|c| c.len() > width as usize / 10)
+        {
+            return i;
+        }
+    }
+    unreachable!()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "p=0,4 v=3,-3
+p=6,3 v=-1,-3
+p=10,3 v=-1,2
+p=2,0 v=2,-1
+p=0,0 v=1,3
+p=3,0 v=-2,-2
+p=7,6 v=-1,-3
+p=3,0 v=-1,-2
+p=9,3 v=2,3
+p=7,3 v=-1,2
+p=2,4 v=2,-3
+p=9,5 v=-3,-3";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1_impl(EXAMPLE, 11, 7), 12);
+    }
+
+    // part 2 does not converge using the test vector
+    // #[test]
+    // fn part2_example() {
+    //     // assert_eq!(part2(EXAMPLE), 0);
+    // }
+}

src/day15.rs

@@ -0,0 +1,241 @@
+use aoc_runner_derive::aoc;
+use grid::{AsCoord2d, Coord2d, Grid};
+use itertools::Itertools;
+use std::{fmt::Display, io::Cursor, str::FromStr};
+
+struct Warehouse {
+    map: Grid<u8>,
+    robot_pos: Coord2d,
+}
+
+impl Display for Warehouse {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.map.fmt(f)
+    }
+}
+
+impl Warehouse {
+    fn step_robot(&mut self, dir: Move) {
+        let start = self.robot_pos;
+        if self.push(&start, &dir) {
+            self.robot_pos = &self.robot_pos + dir.ofs();
+        }
+    }
+
+    fn push(&mut self, pos: &Coord2d, dir: &Move) -> bool {
+        if self.can_push(pos, dir) {
+            let target = pos + dir.ofs();
+            match self.map.get(&target).unwrap() {
+                b'#' => {}
+                b'.' => self.map.swap(target, pos),
+                b'O' => {
+                    self.push(&target, dir);
+                    self.map.swap(target, pos);
+                }
+                b'[' | b']' if *dir == Move::Left || *dir == Move::Right => {
+                    self.push(&target, dir);
+                    self.map.swap(target, pos)
+                }
+                b']' => {
+                    // move both parts
+                    self.push(&target, dir);
+                    self.push(&(&target + (-1, 0)), dir);
+                    self.map.swap(target, pos);
+                }
+                b'[' => {
+                    self.push(&target, dir);
+                    self.push(&(&target + (1, 0)), dir);
+                    self.map.swap(target, pos);
+                }
+                c => panic!("unexpected char {}", c),
+            }
+            return true;
+        }
+        false
+    }
+
+    fn can_push(&mut self, pos: &Coord2d, dir: &Move) -> bool {
+        let target = pos + dir.ofs();
+        match self.map.get(&target).unwrap() {
+            b'#' => false,
+            b'.' => true,
+            b'O' => self.can_push(&target, dir),
+            b'[' | b']' if *dir == Move::Left || *dir == Move::Right => self.can_push(&target, dir),
+            b']' => self.can_push(&target, dir) && self.can_push(&(&target + (-1, 0)), dir),
+            b'[' => self.can_push(&target, dir) && self.can_push(&(&target + (1, 0)), dir),
+            c => panic!("unexpected char {}", c),
+        }
+    }
+
+    fn embiggen(&mut self) {
+        let new_lines = (0..self.map.height())
+            .map(|r| self.map.row(r as i64).unwrap())
+            .map(|row| {
+                row.iter()
+                    .flat_map(|c| match c {
+                        b'#' => ['#', '#'],
+                        b'O' => ['[', ']'],
+                        b'.' => ['.', '.'],
+                        b'@' => ['@', '.'],
+                        c => panic!("unexpected character {}", c),
+                    })
+                    .collect::<String>()
+            })
+            .join("\n");
+        self.map = Grid::from(Cursor::new(new_lines.as_str()));
+        self.robot_pos = self.map.find(&b'@').unwrap().to_coord();
+    }
+
+    fn score(&self) -> i64 {
+        self.map
+            .data
+            .iter()
+            .enumerate()
+            .filter(|(_, v)| **v == b'O' || **v == b'[')
+            .map(|(i, _)| self.map.coord(i as i64).unwrap().y() * 100 + self.map.coord(i as i64).unwrap().x())
+            .sum()
+    }
+}
+
+#[derive(Debug, Eq, PartialEq)]
+enum Move {
+    Left,
+    Right,
+    Up,
+    Down,
+}
+
+impl Display for Move {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Left => f.write_str("Left"),
+            Self::Right => f.write_str("Right"),
+            Self::Up => f.write_str("Up"),
+            Self::Down => f.write_str("Down"),
+        }
+    }
+}
+
+impl From<char> for Move {
+    fn from(c: char) -> Self {
+        match c {
+            '<' => Self::Left,
+            '>' => Self::Right,
+            '^' => Self::Up,
+            'v' => Self::Down,
+            c => panic!("invalid move {}", c),
+        }
+    }
+}
+
+impl Move {
+    fn ofs(&self) -> (i64, i64) {
+        match self {
+            Move::Left => (-1, 0),
+            Move::Right => (1, 0),
+            Move::Up => (0, -1),
+            Move::Down => (0, 1),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct MovePlan(Vec<Move>);
+
+impl FromStr for MovePlan {
+    type Err = Box<dyn std::error::Error>;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(MovePlan(s.chars().filter(|c| *c != '\n').map(Move::from).collect()))
+    }
+}
+
+fn parse(input: &str) -> (Warehouse, MovePlan) {
+    let lines = input.lines().collect_vec();
+    let parts = lines.split(|l| l.is_empty()).map(|ls| ls.join("\n")).collect_vec();
+    let map: Grid<u8> = parts[0].parse().unwrap();
+    let wh = Warehouse {
+        robot_pos: map.find(&b'@').unwrap().to_coord(),
+        map,
+    };
+    let moves = parts[1].parse().unwrap();
+
+    (wh, moves)
+}
+
+#[aoc(day15, part1)]
+pub fn part1(input: &str) -> i64 {
+    let (mut wh, moves) = parse(input);
+    for m in moves.0 {
+        wh.step_robot(m);
+    }
+    wh.score()
+}
+
+#[aoc(day15, part2)]
+pub fn part2(input: &str) -> i64 {
+    let (mut wh, moves) = parse(input);
+    wh.embiggen();
+
+    for m in moves.0 {
+        wh.step_robot(m);
+    }
+    wh.score()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE1: &str = "########
+#..O.O.#
+##@.O..#
+#...O..#
+#.#.O..#
+#...O..#
+#......#
+########
+
+<^^>>>vv<v>>v<<";
+    const EXAMPLE2: &str = "##########
+#..O..O.O#
+#......O.#
+#.OO..O.O#
+#..O@..O.#
+#O#..O...#
+#O..O..O.#
+#.OO.O.OO#
+#....O...#
+##########
+
+<vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
+vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
+><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
+<<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
+^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
+^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
+>^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
+<><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
+^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
+v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^";
+
+    const EXAMPLE3: &str = "#######
+#...#.#
+#.....#
+#..OO@#
+#..O..#
+#.....#
+#######
+
+<vv<<^^<<^^";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE1), 2028);
+        assert_eq!(part1(EXAMPLE2), 10092);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE3), 618);
+        assert_eq!(part2(EXAMPLE2), 9021);
+    }
+}

src/day16.rs

@@ -0,0 +1,294 @@
+use aoc_runner_derive::aoc;
+use grid::{Coord2d, Grid};
+use std::{
+    cmp::Ordering,
+    collections::{BinaryHeap, HashMap},
+    str::FromStr,
+};
+
+type CoordType = i16;
+type Coord = (CoordType, CoordType);
+
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Ord, PartialOrd)]
+enum FacingDirection {
+    East,
+    South,
+    West,
+    North,
+}
+
+impl FacingDirection {
+    fn ofs(&self) -> (CoordType, CoordType) {
+        match self {
+            FacingDirection::East => (1, 0),
+            FacingDirection::South => (0, 1),
+            FacingDirection::West => (-1, 0),
+            FacingDirection::North => (0, -1),
+        }
+    }
+    fn reachable(&self) -> &[FacingDirection; 3] {
+        // Can move perpendicularly or the same direction, backwards would always increase path cost
+        match self {
+            FacingDirection::East => &[FacingDirection::East, FacingDirection::North, FacingDirection::South],
+            FacingDirection::West => &[FacingDirection::West, FacingDirection::North, FacingDirection::South],
+            FacingDirection::South => &[FacingDirection::South, FacingDirection::East, FacingDirection::West],
+            FacingDirection::North => &[FacingDirection::North, FacingDirection::East, FacingDirection::West],
+        }
+    }
+}
+
+#[derive(Clone, Eq, PartialEq, Debug)]
+struct State {
+    cost: usize,
+    position: Coord,
+    facing: FacingDirection,
+}
+
+impl Ord for State {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        other
+            .cost
+            .cmp(&self.cost)
+            .then_with(|| self.position.cmp(&other.position))
+            .then_with(|| self.facing.cmp(&other.facing))
+    }
+}
+
+impl PartialOrd for State {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+#[derive(Clone, Eq, PartialEq, Debug)]
+struct PathState {
+    state: State,
+    path: Vec<Coord>,
+}
+
+impl Ord for PathState {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.state.cmp(&other.state)
+    }
+}
+impl PartialOrd for PathState {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+struct Maze {
+    map: Grid<u8>,
+}
+
+impl FromStr for Maze {
+    type Err = Box<dyn std::error::Error>;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let map: Grid<u8> = s.parse()?;
+
+        Ok(Self { map })
+    }
+}
+
+impl Maze {
+    fn valid_moves<'a>(&'a self, state: &'a State) -> impl Iterator<Item = State> + use<'a> {
+        let reachable = state.facing.reachable();
+        reachable
+            .iter()
+            .map(|dir| (dir, (state.position.0 + dir.ofs().0, state.position.1 + dir.ofs().1)))
+            .filter(|(_, pos)| self.map.get(pos).is_some_and(|c| *c != b'#'))
+            .map(|(dir, pos)| State {
+                facing: *dir,
+                position: pos,
+                cost: if *dir == state.facing {
+                    state.cost + 1
+                } else {
+                    state.cost + 1001
+                },
+            })
+    }
+    fn dijkstra(&self) -> usize {
+        let Coord2d {x: start_x, y: start_y} = self.map.find(&b'S').expect("can't find start");
+        let start = (start_x as CoordType, start_y as CoordType);
+
+        let Coord2d {x: finish_x, y: finish_y} = self.map.find(&b'E').expect("can't find finish");
+        let finish = (finish_x as CoordType, finish_y as CoordType);
+
+        let mut distances = HashMap::new();
+        let mut queue = BinaryHeap::new();
+
+        distances.insert((start, FacingDirection::East), 0);
+        queue.push(State {
+            cost: 0,
+            position: start,
+            facing: FacingDirection::East,
+        });
+
+        while let Some(state) = queue.pop() {
+            if state.position == finish {
+                return state.cost;
+            }
+
+            if distances
+                .get(&(state.position, state.facing))
+                .is_some_and(|v| state.cost > *v)
+            {
+                continue;
+            }
+
+            for new_state in self.valid_moves(&state) {
+                if distances
+                    .get(&(new_state.position, new_state.facing))
+                    .is_none_or(|best_cost| new_state.cost < *best_cost)
+                {
+                    distances.insert((new_state.position, new_state.facing), new_state.cost);
+                    queue.push(new_state);
+                }
+            }
+        }
+        usize::MAX
+    }
+    fn path_dijkstra(&mut self) -> (usize, Vec<Vec<Coord>>) {
+        let Coord2d {x: start_x, y: start_y} = self.map.find(&b'S').expect("can't find start");
+        let start = (start_x as CoordType, start_y as CoordType);
+
+        let Coord2d {x: finish_x, y: finish_y} = self.map.find(&b'E').expect("can't find finish");
+        let finish = (finish_x as CoordType, finish_y as CoordType);
+
+        let mut distances = HashMap::new();
+        let mut queue = BinaryHeap::with_capacity(self.map.data.len());
+        let mut best_paths = Vec::new();
+        let mut best_cost = usize::MAX;
+
+        distances.insert((start, FacingDirection::East), 0);
+        queue.push(PathState {
+            state: State {
+                cost: 0,
+                position: start,
+                facing: FacingDirection::East,
+            },
+            path: Vec::new(),
+        });
+
+        while let Some(PathState { state, mut path }) = queue.pop() {
+            if distances
+                .get(&(state.position, state.facing))
+                .is_some_and(|v| state.cost > *v)
+            {
+                continue;
+            }
+            if state.position == finish {
+                match state.cost.cmp(&best_cost) {
+                    Ordering::Less => {
+                        path.push(state.position);
+                        best_paths.clear();
+                        best_paths.push(path);
+                        best_cost = state.cost
+                    }
+                    Ordering::Equal => {
+                        path.push(state.position);
+                        best_paths.push(path);
+                    }
+                    _ => {}
+                }
+                continue;
+            }
+
+            for new_state in self.valid_moves(&state) {
+                if distances
+                    .get(&(new_state.position, new_state.facing))
+                    .is_none_or(|best_cost| new_state.cost <= *best_cost)
+                {
+                    let mut new_path = path.clone();
+                    new_path.push(state.position);
+                    distances.insert((new_state.position, new_state.facing), new_state.cost);
+                    queue.push(PathState {
+                        state: new_state,
+                        path: new_path,
+                    });
+                }
+            }
+        }
+        (best_cost, best_paths)
+    }
+}
+
+fn parse(input: &str) -> Maze {
+    input.parse().unwrap()
+}
+
+#[aoc(day16, part1)]
+pub fn part1(input: &str) -> usize {
+    let maze = parse(input);
+    maze.dijkstra()
+}
+
+#[aoc(day16, part2)]
+pub fn part2(input: &str) -> usize {
+    let mut maze = parse(input);
+    let best_paths = maze.path_dijkstra();
+
+    let mut path_map = maze.map.same_shape(false);
+    for tile in best_paths.1.iter().flatten() {
+        path_map.set(tile, true);
+    }
+    path_map.count(&true)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE1: &str = "###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############";
+
+    const EXAMPLE2: &str = "#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################";
+
+    #[test]
+    fn part1_example1() {
+        assert_eq!(part1(EXAMPLE1), 7036);
+    }
+
+    #[test]
+    fn part1_example2() {
+        assert_eq!(part1(EXAMPLE2), 11048);
+    }
+
+    #[test]
+    fn part2_example1() {
+        assert_eq!(part2(EXAMPLE1), 45);
+    }
+
+    #[test]
+    fn part2_example2() {
+        assert_eq!(part2(EXAMPLE2), 64);
+    }
+}

src/day17.rs

@@ -0,0 +1,298 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use regex::Regex;
+
+#[derive(Debug, Clone, Copy)]
+enum Register {
+    A = 0,
+    B = 1,
+    C = 2,
+}
+impl From<usize> for Register {
+    fn from(value: usize) -> Self {
+        match value {
+            0 => Register::A,
+            1 => Register::B,
+            2 => Register::C,
+            v => panic!("invalid register address {}", v),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+enum Opcode {
+    Adv = 0,
+    Bxl = 1,
+    Bst = 2,
+    Jnz = 3,
+    Bxc = 4,
+    Out = 5,
+    Bdv = 6,
+    Cdv = 7,
+}
+
+impl From<i64> for Opcode {
+    fn from(value: i64) -> Self {
+        match value {
+            0 => Opcode::Adv,
+            1 => Opcode::Bxl,
+            2 => Opcode::Bst,
+            3 => Opcode::Jnz,
+            4 => Opcode::Bxc,
+            5 => Opcode::Out,
+            6 => Opcode::Bdv,
+            7 => Opcode::Cdv,
+            v => panic!("invalid opcode {}", v),
+        }
+    }
+}
+
+impl Opcode {
+    fn interp_operand(&self, value: i64) -> Operand {
+        match self {
+            Self::Adv | Self::Bst | Self::Out | Self::Bdv | Self::Cdv => Operand::new_combo(value),
+            Self::Bxl | Self::Jnz => Operand::Literal(value),
+            Self::Bxc => Operand::Ignore,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+enum Operand {
+    Literal(i64),
+    Load(Register),
+    Ignore,
+}
+
+impl Operand {
+    fn new_combo(value: i64) -> Self {
+        match value {
+            0..=3 => Operand::Literal(value),
+            4 => Operand::Load(Register::A),
+            5 => Operand::Load(Register::B),
+            6 => Operand::Load(Register::C),
+            7 => panic!("reserved combo operand 7"),
+            i => panic!("invalid combo operand {}", i),
+        }
+    }
+    fn value(self, m: &Machine) -> i64 {
+        match self {
+            Self::Literal(i) => i,
+            Self::Load(reg) => *m.registers.load(reg),
+            Self::Ignore => panic!("can't read ignored operand"),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct RegisterFile<const SIZE: usize, T> {
+    file: [T; SIZE],
+}
+
+impl<T: Clone + From<i64>, const SIZE: usize> RegisterFile<SIZE, T> {
+    fn load(&self, reg: Register) -> &T {
+        &self.file[reg as usize]
+    }
+    fn store(&mut self, reg: Register, val: T) {
+        self.file[reg as usize] = val;
+    }
+    fn reset(&mut self) {
+        self.file.fill(0.into());
+    }
+}
+
+#[derive(Debug, Copy, Clone)]
+struct Instruction {
+    opcode: Opcode,
+    operand: Operand,
+}
+
+impl Instruction {
+    fn exec(&self, m: &mut Machine) {
+        match self.opcode {
+            Opcode::Adv => self.adv(m),
+            Opcode::Bxl => self.bxl(m),
+            Opcode::Bst => self.bst(m),
+            Opcode::Jnz => self.jnz(m),
+            Opcode::Bxc => self.bxc(m),
+            Opcode::Out => self.out(m),
+            Opcode::Bdv => self.bdv(m),
+            Opcode::Cdv => self.cdv(m),
+        }
+    }
+    fn adv(&self, m: &mut Machine) {
+        let num = m.registers.load(Register::A);
+        let denom = 1 << self.operand.value(m);
+        m.registers.store(Register::A, num / denom);
+        m.advance();
+    }
+    fn bxl(&self, m: &mut Machine) {
+        let lhs = self.operand.value(m);
+        let rhs = m.registers.load(Register::B);
+        m.registers.store(Register::B, lhs ^ rhs);
+        m.advance();
+    }
+    fn bst(&self, m: &mut Machine) {
+        m.registers.store(Register::B, self.operand.value(m) % 8);
+        m.advance();
+    }
+    fn jnz(&self, m: &mut Machine) {
+        if *m.registers.load(Register::A) == 0 {
+            m.advance();
+        } else {
+            m.jump(self.operand.value(m) as usize);
+        }
+    }
+    fn bxc(&self, m: &mut Machine) {
+        let lhs = m.registers.load(Register::B);
+        let rhs = m.registers.load(Register::C);
+        m.registers.store(Register::B, lhs ^ rhs);
+        m.advance();
+    }
+    fn out(&self, m: &mut Machine) {
+        m.out_file.push(self.operand.value(m) % 8);
+        m.advance();
+    }
+    fn bdv(&self, m: &mut Machine) {
+        let num = m.registers.load(Register::A);
+        let denom = 1 << self.operand.value(m);
+        m.registers.store(Register::B, num / denom);
+        m.advance();
+    }
+    fn cdv(&self, m: &mut Machine) {
+        let num = m.registers.load(Register::A);
+        let denom = 1 << self.operand.value(m);
+        m.registers.store(Register::C, num / denom);
+        m.advance();
+    }
+}
+
+#[derive(Debug)]
+pub struct Machine {
+    registers: RegisterFile<3, i64>,
+    program: Vec<Instruction>,
+    program_raw: Vec<i64>,
+    ip: usize,
+    out_file: Vec<i64>,
+}
+
+impl Machine {
+    fn run(&mut self) {
+        let program = self.program.clone();
+        while let Some(inst) = program.get(self.ip) {
+            inst.exec(self);
+        }
+    }
+    fn advance(&mut self) {
+        self.ip += 1;
+    }
+    fn jump(&mut self, addr: usize) {
+        self.ip = addr;
+    }
+    fn reset(&mut self) {
+        self.registers.reset();
+        self.ip = 0;
+        self.out_file.clear();
+    }
+}
+
+fn parse(input: &str) -> Machine {
+    let reg_re = Regex::new(r"Register ([ABC]): (\d+)").unwrap();
+    let prog_re = Regex::new(r"Program: ((\d+,)*\d+)").unwrap();
+
+    let mut registers: RegisterFile<3, i64> = RegisterFile { file: [0; 3] };
+    let mut program = Vec::new();
+    let mut program_raw = Vec::new();
+    for line in input.lines() {
+        if let Some(caps) = reg_re.captures(line) {
+            let address = (caps[1].as_bytes()[0] - b'A') as usize;
+            let value = caps[2].parse().unwrap();
+            registers.store(address.into(), value);
+            continue;
+        }
+        if let Some(caps) = prog_re.captures(line) {
+            let instructions = caps[1].split(',');
+            for (inst, operand) in instructions.tuples() {
+                let opcode = inst.parse::<i64>().unwrap();
+                let operand = operand.parse::<i64>().unwrap();
+                program_raw.push(opcode);
+                program_raw.push(operand);
+                let opcode: Opcode = opcode.into();
+                program.push(Instruction {
+                    operand: opcode.interp_operand(operand),
+                    opcode,
+                });
+            }
+        }
+    }
+
+    Machine {
+        registers,
+        program,
+        program_raw,
+        out_file: Vec::new(),
+        ip: 0,
+    }
+}
+
+#[aoc(day17, part1)]
+pub fn part1(input: &str) -> String {
+    let mut machine = parse(input);
+    machine.run();
+    machine.out_file.iter().map(|n| n.to_string()).join(",")
+}
+
+// The program must be of the correct form to be solvable
+pub fn solve(m: &mut Machine, guess: i64, i: usize) -> Option<i64> {
+    if i == m.program_raw.len() {
+        return Some(guess);
+    }
+    let program_pos = m.program_raw.len() - 1 - i;
+    let goal_digit = m.program_raw[program_pos];
+
+    for digit in 0..8 {
+        let local_guess = (digit << (program_pos * 3)) + guess;
+        m.reset();
+        m.registers.store(Register::A, local_guess);
+        m.run();
+        if m.out_file.len() == m.program_raw.len() && m.out_file[program_pos] == goal_digit {
+            if let Some(sol) = solve(m, local_guess, i + 1) {
+                return Some(sol);
+            }
+        }
+    }
+    None
+}
+
+#[aoc(day17, part2)]
+pub fn part2(input: &str) -> i64 {
+    let mut machine = parse(input);
+
+    solve(&mut machine, 0, 0).expect("expected a solution")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE1: &str = "Register A: 729
+Register B: 0
+Register C: 0
+
+Program: 0,1,5,4,3,0";
+
+    const EXAMPLE2: &str = "Register A: 2024
+Register B: 0
+Register C: 0
+
+Program: 0,3,5,4,3,0";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE1), "4,6,3,5,6,3,5,2,1,0");
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE2), 117440);
+    }
+}

src/day18.rs

@@ -0,0 +1,286 @@
+use aoc_runner_derive::aoc;
+use grid::Grid;
+use itertools::Itertools;
+use std::{
+    cmp::Reverse,
+    collections::{BinaryHeap, VecDeque},
+};
+
+#[derive(Clone)]
+struct MemoryMap {
+    map: Grid<bool>,
+    byte_stream: Vec<(i64, i64)>,
+}
+
+trait PathTrack {
+    const DOES_WORK: bool = true;
+    fn new() -> Self;
+    fn push(&mut self, pos: (i64, i64));
+    fn finalize(&mut self) {}
+}
+
+struct LengthPath(usize);
+impl PathTrack for LengthPath {
+    fn new() -> Self {
+        LengthPath(0)
+    }
+    fn push(&mut self, _: (i64, i64)) {
+        self.0 += 1
+    }
+}
+
+impl PathTrack for Vec<(i64, i64)> {
+    fn new() -> Self {
+        Vec::new()
+    }
+    fn push(&mut self, pos: (i64, i64)) {
+        self.push(pos);
+    }
+    fn finalize(&mut self) {
+        self.reverse();
+    }
+}
+
+struct NoopTrack {}
+impl PathTrack for NoopTrack {
+    const DOES_WORK: bool = false;
+    fn new() -> Self {
+        Self {}
+    }
+    fn push(&mut self, _: (i64, i64)) {}
+}
+
+impl MemoryMap {
+    fn from_str(input: &str, width: usize, height: usize) -> Self {
+        let map = Grid::with_shape(width, height, true);
+        let mut byte_stream = Vec::new();
+
+        for line in input.lines() {
+            if let Some((x, y)) = line.split_once(',') {
+                let pos: (i64, i64) = (x.parse().unwrap(), y.parse().unwrap());
+                byte_stream.push(pos);
+            }
+        }
+
+        Self { map, byte_stream }
+    }
+
+    fn place_byte(&mut self, i: usize) {
+        let pos = self.byte_stream[i];
+        self.map.set(&pos, false);
+    }
+
+    fn place_bytes(&mut self, start: usize, end: usize) {
+        for i in start..=end {
+            self.place_byte(i);
+        }
+    }
+
+    fn valid_moves<'a>(&'a self, pos: &'a (i64, i64)) -> impl Iterator<Item = (i64, i64)> + 'a {
+        ([(0, 1), (1, 0), (0, -1), (-1, 0)])
+            .iter()
+            .filter(|ofs| self.map.get(&(pos.0 + ofs.0, pos.1 + ofs.1)).is_some_and(|v| *v))
+            .map(|ofs| (pos.0 + ofs.0, pos.1 + ofs.1))
+    }
+
+    fn bfs<T: PathTrack>(&self, start: (i64, i64)) -> Option<T> {
+        let goal = (self.map.width() as i64 - 1, self.map.height() as i64 - 1);
+
+        let mut visited = self.map.same_shape(false);
+        let mut prev = self.map.same_shape((i64::MAX, i64::MAX));
+        let mut queue = VecDeque::new();
+
+        visited.set(&start, true);
+        queue.push_back((0, start));
+
+        while let Some((depth, pos)) = queue.pop_front() {
+            if pos == goal {
+                if T::DOES_WORK {
+                    let mut visited_pos = goal;
+                    let mut path = T::new();
+                    path.push(pos);
+                    while let Some(next) = prev.get(&visited_pos) {
+                        visited_pos = *next;
+                        path.push(*next);
+                        if *next == start {
+                            path.finalize();
+                            return Some(path);
+                        }
+                    }
+                } else {
+                    return Some(T::new());
+                }
+            }
+
+            // if visited.get(&pos).is_some_and(|v| *v) {
+            //     continue;
+            // }
+
+            let moves = self.valid_moves(&pos);
+            for new_pos in moves {
+                if visited.get(&new_pos).is_none_or(|v| !v) {
+                    visited.set(&new_pos, true);
+                    if T::DOES_WORK {
+                        prev.set(&new_pos, pos);
+                    }
+                    queue.push_back((depth + 1, new_pos));
+                }
+            }
+        }
+        None
+    }
+
+    #[allow(dead_code)] // will be moved to Grid at some point
+    fn dijkstra<T: PathTrack>(&self, start: (i64, i64)) -> Option<T> {
+        let goal = (self.map.width() as i64 - 1, self.map.height() as i64 - 1);
+
+        let mut costs = self.map.same_shape(i64::MAX);
+        let mut prev = self.map.same_shape((i64::MAX, i64::MAX));
+        let mut queue = BinaryHeap::new();
+
+        costs.set(&start, 0);
+        queue.push((Reverse(0), start));
+
+        while let Some((cost, pos)) = queue.pop() {
+            if pos == goal {
+                if T::DOES_WORK {
+                    let mut visited_pos = goal;
+                    let mut path = T::new();
+                    path.push(pos);
+                    while let Some(next) = prev.get(&visited_pos) {
+                        visited_pos = *next;
+                        path.push(*next);
+                        if *next == start {
+                            path.finalize();
+                            return Some(path);
+                        }
+                    }
+                } else {
+                    return Some(T::new());
+                }
+            }
+
+            if costs.get(&pos).is_some_and(|v| cost.0 > *v) {
+                continue;
+            }
+
+            let moves = self.valid_moves(&pos);
+            for new_pos in moves {
+                if costs.get(&new_pos).is_none_or(|best_cost| cost.0 + 1 < *best_cost) {
+                    costs.set(&new_pos, cost.0 + 1);
+                    if T::DOES_WORK {
+                        prev.set(&new_pos, pos);
+                    }
+                    queue.push((Reverse(cost.0 + 1), new_pos));
+                }
+            }
+        }
+        None
+    }
+}
+
+pub fn part1_impl(input: &str, width: usize, height: usize, initial_safe_byte_count: usize) -> usize {
+    let mut map = MemoryMap::from_str(input, width, height);
+    map.place_bytes(0, initial_safe_byte_count - 1);
+    let path = map.bfs::<LengthPath>((0, 0)).expect("no path found");
+
+    path.0 - 1 // count edges, not visited nodes (start doesn't count)
+}
+
+// My original devised solution
+pub fn part2_impl_brute(input: &str, width: usize, height: usize, initial_safe_byte_count: usize) -> (i64, i64) {
+    let mut input_map = MemoryMap::from_str(input, width, height);
+    input_map.place_bytes(0, initial_safe_byte_count - 1);
+
+    let mut path = input_map.bfs::<Vec<(i64, i64)>>((0, 0)).expect("no path found");
+
+    for byte in initial_safe_byte_count..input_map.byte_stream.len() {
+        input_map.place_byte(byte);
+        // If it obstructs our best path, we need to do a new path search
+        if let Some((obs_at, _)) = path.iter().find_position(|v| *v == &input_map.byte_stream[byte]) {
+            let (before, _) = path.split_at(obs_at);
+
+            if let Some(new_path) = input_map.bfs::<Vec<(i64, i64)>>(path[obs_at - 1]) {
+                path = [before, &new_path].concat();
+            } else {
+                return input_map.byte_stream[byte];
+            }
+        }
+    }
+    panic!("no bytes block route");
+}
+
+// Optimized based on others' ideas
+pub fn part2_impl(input: &str, width: usize, height: usize, initial_safe_byte_count: usize) -> (i64, i64) {
+    let mut input_map = MemoryMap::from_str(input, width, height);
+
+    input_map.place_bytes(0, initial_safe_byte_count - 1);
+
+    // for the unplaced bytes, binary search for the partition point, given the predicate that a path is reachable
+    // when all bytes up to that n have been placed
+    let possible_problems = (initial_safe_byte_count..input_map.byte_stream.len()).collect_vec();
+    let solution = possible_problems.partition_point(|byte| {
+        // avoiding this clone by rolling back the byte placements instead is slower
+        let mut local_map = input_map.clone();
+        local_map.place_bytes(initial_safe_byte_count, *byte);
+        local_map.bfs::<NoopTrack>((0, 0)).is_some()
+    }) + initial_safe_byte_count;
+
+    input_map.byte_stream[solution]
+}
+
+#[aoc(day18, part1)]
+pub fn part1(input: &str) -> usize {
+    part1_impl(input, 71, 71, 1024)
+}
+
+#[aoc(day18, part2)]
+pub fn part2(input: &str) -> String {
+    let sol = part2_impl(input, 71, 71, 1024);
+    format!("{},{}", sol.0, sol.1)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1_impl(EXAMPLE, 7, 7, 12), 22);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2_impl(EXAMPLE, 7, 7, 12), (6, 1));
+    }
+
+    #[test]
+    fn part2_example_brute() {
+        assert_eq!(part2_impl_brute(EXAMPLE, 7, 7, 12,), (6, 1));
+    }
+}

src/day19.rs

@@ -0,0 +1,192 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use rayon::iter::{IntoParallelIterator, ParallelIterator};
+use rustc_hash::FxHashMap;
+use std::fmt::{Display, Write};
+
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+enum Stripe {
+    White = b'w',
+    Blue = b'u',
+    Black = b'b',
+    Red = b'r',
+    Green = b'g',
+}
+
+impl From<&u8> for Stripe {
+    fn from(value: &u8) -> Self {
+        match value {
+            b'w' => Self::White,
+            b'u' => Self::Blue,
+            b'b' => Self::Black,
+            b'r' => Self::Red,
+            b'g' => Self::Green,
+            _ => unimplemented!(),
+        }
+    }
+}
+
+impl From<&Stripe> for char {
+    fn from(val: &Stripe) -> Self {
+        let v = *val as u8;
+        v.into()
+    }
+}
+
+impl Display for Stripe {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_char(self.into())
+    }
+}
+
+#[derive(Debug, Clone)]
+struct Design {
+    stripes: Vec<Stripe>,
+}
+
+impl From<&[u8]> for Design {
+    fn from(input: &[u8]) -> Self {
+        let stripes = input.iter().map(|c| c.into()).collect();
+        Self { stripes }
+    }
+}
+
+impl Display for Design {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for stripe in &self.stripes {
+            f.write_char(stripe.into())?;
+        }
+        Ok(())
+    }
+}
+
+#[derive(Debug)]
+struct Onsen {
+    towels: Vec<Design>,
+    designs: Vec<Design>,
+}
+
+impl Display for Onsen {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.towels.iter().join(", "))?;
+        writeln!(f)?;
+        writeln!(f)?;
+        for d in &self.designs {
+            d.fmt(f)?;
+            writeln!(f)?;
+        }
+        Ok(())
+    }
+}
+
+impl Onsen {
+    fn possible(&self, d: &[Stripe]) -> bool {
+        if d.is_empty() {
+            return true;
+        }
+        for t in &self.towels {
+            if d.starts_with(&t.stripes) && self.possible(d.split_at(t.stripes.len()).1) {
+                return true;
+            }
+        }
+        false
+    }
+    // Count the ways to construct a given substring
+    fn ways<'a>(
+        &'a self,
+        d: &'a [Stripe],
+        mut cache: FxHashMap<&'a [Stripe], i64>,
+    ) -> (FxHashMap<&'a [Stripe], i64>, i64) {
+        if d.is_empty() {
+            return (cache, 1);
+        }
+        if cache.contains_key(d) {
+            let val = cache[d];
+            return (cache, val);
+        }
+
+        let mut count = 0;
+        for t in &self.towels {
+            if d.starts_with(&t.stripes) {
+                let res_count;
+                (cache, res_count) = self.ways(&d[t.stripes.len()..d.len()], cache);
+                count += res_count;
+            }
+        }
+        cache.insert(d, count);
+        (cache, count)
+    }
+    fn count_possible(&self) -> i64 {
+        self.designs
+            .clone()
+            .into_par_iter()
+            .map(|d| self.possible(&d.stripes))
+            .filter(|p| *p)
+            .count() as i64
+    }
+    fn count_ways(&self) -> i64 {
+        self.designs
+            .clone()
+            .into_par_iter()
+            .map(|d| self.ways(&d.stripes, FxHashMap::default()).1)
+            .sum::<i64>()
+    }
+}
+
+fn parse(input: &str) -> Onsen {
+    let mut lines = input.lines();
+
+    let towels = lines
+        .next()
+        .unwrap()
+        .split(&[',', ' '])
+        .filter(|s| !s.is_empty())
+        .map(|s| s.as_bytes().into())
+        .collect();
+
+    lines.next().unwrap(); // discard empty line
+
+    let designs = lines.map(|l| l.as_bytes().into()).collect();
+
+    Onsen { towels, designs }
+}
+
+#[aoc(day19, part1)]
+fn part1(input: &str) -> i64 {
+    let onsen = parse(input);
+
+    onsen.count_possible()
+}
+
+#[aoc(day19, part2)]
+fn part2(input: &str) -> i64 {
+    let onsen = parse(input);
+
+    onsen.count_ways()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 6);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE), 16);
+    }
+}

src/day2.rs

@@ -0,0 +1,105 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use std::io::{BufRead, Lines};
+
+#[aoc_generator(day2)]
+pub fn get_input(input: &[u8]) -> Reports {
+    Reports::from(input.lines())
+}
+
+#[derive(Debug)]
+pub struct Reports {
+    reports: Vec<Vec<u64>>,
+}
+
+impl<T: BufRead> From<Lines<T>> for Reports {
+    fn from(lines: Lines<T>) -> Self {
+        let mut reports = Vec::new();
+        for line in lines.map(|i| i.unwrap()) {
+            reports.push(
+                line.split_ascii_whitespace()
+                    .map(|record| record.parse::<u64>().unwrap())
+                    .collect(),
+            )
+        }
+        Reports { reports }
+    }
+}
+
+impl Reports {
+    fn is_safe(report: &[u64]) -> bool {
+        let mut ascending: bool = true;
+        let mut descending: bool = true;
+        for (a, b) in report.iter().zip(report.iter().skip(1)) {
+            if a > b {
+                ascending = false
+            }
+            if a < b {
+                descending = false;
+            }
+            let ad = a.abs_diff(*b);
+            if !(1..=3).contains(&ad) || (!ascending && !descending) {
+                return false;
+            };
+        }
+        true
+    }
+    fn count_safe(&self) -> u64 {
+        self.reports.iter().filter(|report| Self::is_safe(report)).count() as u64
+    }
+    fn is_dumb_dampened_safe(report: &[u64]) -> bool {
+        if Self::is_safe(report) {
+            return true;
+        }
+        for i in 0..report.len() {
+            let mut new_vec = report.to_owned();
+            new_vec.remove(i);
+            if Self::is_safe(&new_vec) {
+                return true;
+            }
+        }
+        false
+    }
+    fn dampened_count_safe(&self) -> u64 {
+        self.reports
+            .iter()
+            .filter(|report| Self::is_dumb_dampened_safe(report))
+            .count() as u64
+    }
+}
+
+// PROBLEM 1 solution
+#[aoc(day2, part1)]
+pub fn part1(input: &Reports) -> u64 {
+    input.count_safe()
+}
+
+// PROBLEM 2 solution
+#[aoc(day2, part2)]
+pub fn part2(input: &Reports) -> u64 {
+    input.dampened_count_safe()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day2::*;
+
+    const EXAMPLE: &[u8] = b"7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9";
+
+    #[test]
+    fn part1_example() {
+        let input = get_input(EXAMPLE);
+        println!("{:?}", input);
+        assert_eq!(part1(&input), 2);
+    }
+
+    #[test]
+    fn part2_example() {
+        let input = get_input(EXAMPLE);
+        assert_eq!(part2(&input), 4);
+    }
+}

src/day20.rs

@@ -0,0 +1,186 @@
+use aoc_runner_derive::aoc;
+use grid::{AsCoord2d, Coord2d, Grid};
+use itertools::Itertools;
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+use std::collections::VecDeque;
+
+struct RaceTrack {
+    map: Grid<u8>,
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+struct State {
+    pos: Coord2d,
+    cost: u64,
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+struct CheatState {
+    s: State,
+}
+
+const DIRECTIONS: [(i64, i64); 4] = [(-1, 0), (1, 0), (0, -1), (0, 1)];
+
+impl RaceTrack {
+    fn valid_moves<'a>(&'a self, CheatState { s: state }: &'a CheatState) -> impl Iterator<Item = CheatState> + 'a {
+        DIRECTIONS
+            .iter()
+            .map(|dir| state.pos + dir)
+            .filter_map(move |pos| match &self.map.get(&pos) {
+                Some(b'.') | Some(b'S') | Some(b'E') => Some(CheatState {
+                    s: State {
+                        pos,
+                        cost: state.cost + 1,
+                    },
+                }),
+                _ => None,
+            })
+    }
+    fn path_costs(&self, start: Coord2d, goal: Coord2d) -> Grid<Option<u64>> {
+        let mut queue = VecDeque::new();
+        let mut visited = self.map.same_shape(None);
+
+        let start_state = CheatState {
+            s: State { pos: start, cost: 0 },
+        };
+        visited.set(&start, Some(0));
+        queue.push_back(start_state);
+
+        while let Some(state) = queue.pop_front() {
+            if state.s.pos == goal {
+                return visited;
+            }
+
+            let moves = self.valid_moves(&state);
+            for new_state in moves {
+                if visited.get(&new_state.s.pos).unwrap().is_some() {
+                    continue;
+                }
+                visited.set(&new_state.s.pos, Some(new_state.s.cost));
+                queue.push_back(new_state);
+            }
+        }
+        panic!("no path");
+    }
+
+    fn find_cheats(&self, path: &Vec<Coord2d>, costs: &Grid<Option<u64>>, min: u64) -> i64 {
+        let mut n = 0;
+        for pos in path {
+            let local_cost = costs.get(pos).unwrap().unwrap();
+            for ofs in DIRECTIONS {
+                let cheat_exit = (pos.x() + ofs.0 * 2, pos.y() + ofs.1 * 2);
+                if let Some(Some(cheat_cost)) = costs.get(&cheat_exit) {
+                    if *cheat_cost > local_cost + 2 {
+                        let cheat_savings = cheat_cost - local_cost - 2;
+                        if cheat_savings >= min {
+                            n += 1;
+                        }
+                    }
+                }
+            }
+        }
+        n
+    }
+
+    fn taxi_dist<A: AsCoord2d, B: AsCoord2d>(from: &A, to: &B) -> u64 {
+        from.x().abs_diff(to.x()) + from.y().abs_diff(to.y())
+    }
+
+    fn find_cheats_n(&self, path: &Vec<Coord2d>, costs: &Grid<Option<u64>>, max_length: u64, min: u64) -> i64 {
+        path.par_iter()
+            .map_with(costs, |costs, pos| {
+                let from_cost = costs.get(pos).unwrap().unwrap();
+                let mut n = 0;
+                for x in pos.x - max_length as i64 - 1..=pos.x + max_length as i64 {
+                    for y in pos.y - max_length as i64 - 1..=pos.y + max_length as i64 {
+                        let dist = Self::taxi_dist(pos, &(x, y));
+                        if dist <= max_length && dist >= 2 {
+                            if let Some(Some(to_cost)) = costs.get(&(x, y)) {
+                                if *to_cost > (from_cost + dist) && (to_cost - (from_cost + dist) >= min) {
+                                    n += 1;
+                                }
+                            }
+                        }
+                    }
+                }
+                n
+            })
+            .sum()
+    }
+}
+
+fn parse(input: &str) -> RaceTrack {
+    let map = input.as_bytes().into();
+    RaceTrack { map }
+}
+
+fn part1_impl(input: &str, cheat_min: u64) -> i64 {
+    let track = parse(input);
+    let start = track.map.find(&b'S').unwrap();
+    let goal = track.map.find(&b'E').unwrap();
+    let costs = track.path_costs(start, goal);
+    let path_squares = costs
+        .data
+        .iter()
+        .enumerate()
+        .filter(|(_i, c)| c.is_some())
+        .filter_map(|(i, _)| track.map.coord(i as i64))
+        .collect_vec();
+    track.find_cheats(&path_squares, &costs, cheat_min)
+}
+
+fn part2_impl(input: &str, max_length: u64, cheat_min: u64) -> i64 {
+    let track = parse(input);
+    let start = track.map.find(&b'S').unwrap();
+    let goal = track.map.find(&b'E').unwrap();
+    let costs = track.path_costs(start, goal);
+    let path_squares = costs
+        .data
+        .iter()
+        .enumerate()
+        .filter(|(_i, c)| c.is_some())
+        .filter_map(|(i, _)| track.map.coord(i as i64))
+        .collect_vec();
+    track.find_cheats_n(&path_squares, &costs, max_length, cheat_min)
+}
+
+#[aoc(day20, part1)]
+pub fn part1(input: &str) -> i64 {
+    part1_impl(input, 100)
+}
+
+#[aoc(day20, part2)]
+pub fn part2(input: &str) -> i64 {
+    part2_impl(input, 20, 100)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "###############
+#...#...#.....#
+#.#.#.#.#.###.#
+#S#...#.#.#...#
+#######.#.#.###
+#######.#.#...#
+#######.#.###.#
+###..E#...#...#
+###.#######.###
+#...###...#...#
+#.#####.#.###.#
+#.#...#.#.#...#
+#.#.#.#.#.#.###
+#...#...#...###
+###############";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1_impl(EXAMPLE, 0), 44);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2_impl(EXAMPLE, 2, 0), 44);
+        assert_eq!(part2_impl(EXAMPLE, 20, 50), 285);
+    }
+}

src/day21.rs

@@ -0,0 +1,240 @@
+use aoc_runner_derive::aoc;
+use rustc_hash::FxHashMap;
+use std::iter::repeat_n;
+
+#[derive(Clone, Debug)]
+enum KeypadRobot {
+    Number(NumberKeypadRobot),
+    Direction(DirectionKeypadRobot),
+}
+
+impl KeypadRobot {
+    fn press(&mut self, target: u8) -> Vec<FxHashMap<Vec<u8>, usize>> {
+        match self {
+            Self::Number(r) => r.press(target),
+            Self::Direction(r) => r.press(target),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+struct NumberKeypadRobot {
+    pointing_at: u8,
+}
+
+impl NumberKeypadRobot {
+    fn pos_of(button: u8) -> (i8, i8) {
+        match button {
+            b'7' => (0, 0),
+            b'8' => (1, 0),
+            b'9' => (2, 0),
+            b'4' => (0, 1),
+            b'5' => (1, 1),
+            b'6' => (2, 1),
+            b'1' => (0, 2),
+            b'2' => (1, 2),
+            b'3' => (2, 2),
+            b'X' => (0, 3),
+            b'0' => (1, 3),
+            b'A' => (2, 3),
+            c => unimplemented!("unexpected character {}", c),
+        }
+    }
+}
+impl NumberKeypadRobot {
+    fn new() -> Self {
+        Self { pointing_at: b'A' }
+    }
+    fn press(&mut self, target: u8) -> Vec<FxHashMap<Vec<u8>, usize>> {
+        let cur_pos = Self::pos_of(self.pointing_at);
+        let goal_pos = Self::pos_of(target);
+        let x_ofs = goal_pos.0 - cur_pos.0;
+        let y_ofs = goal_pos.1 - cur_pos.1;
+
+        let mut paths = Vec::new();
+        // NOTE: no need to consider zig-zags since those paths will always require more button presses going back and forth
+        if (cur_pos.0 + x_ofs, cur_pos.1) != Self::pos_of(b'X') {
+            let mut x_first = Vec::new();
+            x_first.extend(repeat_n(if x_ofs > 0 { b'>' } else { b'<' }, x_ofs.abs() as usize));
+            x_first.extend(repeat_n(if y_ofs > 0 { b'v' } else { b'^' }, y_ofs.abs() as usize));
+            x_first.push(b'A');
+            paths.push({
+                let mut h = FxHashMap::default();
+                h.insert(x_first, 1);
+                h
+            });
+        }
+        if (cur_pos.0, cur_pos.1 + y_ofs) != Self::pos_of(b'X') {
+            let mut y_first = Vec::new();
+            y_first.extend(repeat_n(if y_ofs > 0 { b'v' } else { b'^' }, y_ofs.abs() as usize));
+            y_first.extend(repeat_n(if x_ofs > 0 { b'>' } else { b'<' }, x_ofs.abs() as usize));
+            y_first.push(b'A');
+            paths.push({
+                let mut h = FxHashMap::default();
+                h.insert(y_first, 1);
+                h
+            });
+        }
+        if paths.is_empty() {
+            panic!("all paths lead to the void");
+        }
+        paths.dedup();
+        self.pointing_at = target;
+        paths
+    }
+}
+
+#[derive(Clone, Debug)]
+struct DirectionKeypadRobot {
+    pointing_at: u8,
+    child: Option<Box<KeypadRobot>>,
+    id: usize,
+}
+
+impl DirectionKeypadRobot {
+    fn pos_of(target: u8) -> (i8, i8) {
+        match target {
+            b'X' => (0, 0),
+            b'^' => (1, 0),
+            b'A' => (2, 0),
+            b'<' => (0, 1),
+            b'v' => (1, 1),
+            b'>' => (2, 1),
+            c => unimplemented!("unexpected char {}", c),
+        }
+    }
+    fn move_to(&mut self, target: u8) -> Vec<u8> {
+        let cur_pos = Self::pos_of(self.pointing_at);
+        let goal_pos = Self::pos_of(target);
+        let x_ofs = goal_pos.0 - cur_pos.0;
+        let y_ofs = goal_pos.1 - cur_pos.1;
+
+        self.pointing_at = target;
+
+        if (cur_pos.0 + x_ofs, cur_pos.1) != Self::pos_of(b'X') {
+            let mut x_first = Vec::new();
+            x_first.extend(repeat_n(if x_ofs > 0 { b'>' } else { b'<' }, x_ofs.abs() as usize));
+            x_first.extend(repeat_n(if y_ofs > 0 { b'v' } else { b'^' }, y_ofs.abs() as usize));
+            x_first.push(b'A');
+            return x_first;
+        }
+        if (cur_pos.0, cur_pos.1 + y_ofs) != Self::pos_of(b'X') {
+            let mut y_first = Vec::new();
+            y_first.extend(repeat_n(if y_ofs > 0 { b'v' } else { b'^' }, y_ofs.abs() as usize));
+            y_first.extend(repeat_n(if x_ofs > 0 { b'>' } else { b'<' }, x_ofs.abs() as usize));
+            y_first.push(b'A');
+            return y_first;
+        }
+        panic!("all routes lead to the void");
+    }
+    fn path_to(&mut self, moves: &Vec<u8>) -> Vec<u8> {
+        let prev_point = self.pointing_at;
+        let mut path = Vec::new();
+        for m in moves {
+            path.append(&mut self.move_to(*m));
+        }
+        self.pointing_at = prev_point;
+        path
+    }
+
+    fn new(id: usize, child: Option<Box<KeypadRobot>>) -> Self {
+        Self {
+            id,
+            pointing_at: b'A',
+            child,
+        }
+    }
+    fn press(&mut self, target: u8) -> Vec<FxHashMap<Vec<u8>, usize>> {
+        let child_frequencies = self.child.as_mut().unwrap().press(target);
+        let mut my_frequencies = Vec::new();
+
+        for freq_set in child_frequencies {
+            let mut local_freqs = FxHashMap::default();
+            for (moves, count) in freq_set {
+                assert_eq!(self.pointing_at, b'A');
+                let path = self.path_to(&moves);
+                for path_move in path.split_inclusive(|m| *m == b'A') {
+                    let entry = local_freqs.entry(path_move.to_vec()).or_insert(0);
+                    *entry = *entry + count;
+                }
+            }
+            my_frequencies.push(local_freqs);
+        }
+        my_frequencies
+    }
+}
+
+struct Code(Vec<u8>);
+
+impl Code {
+    fn num_val(&self) -> i64 {
+        String::from_utf8_lossy(&self.0.as_slice()[0..3]).parse().unwrap()
+    }
+}
+
+fn parse(input: &str) -> Vec<Code> {
+    let mut codes = Vec::new();
+    for code in input.lines() {
+        codes.push(Code(code.as_bytes().to_vec()))
+    }
+    codes
+}
+
+fn run_robots(code: &Code, n: usize) -> i64 {
+    let numpad = Box::new(KeypadRobot::Number(NumberKeypadRobot::new()));
+
+    let mut robot = Box::new(KeypadRobot::Direction(DirectionKeypadRobot::new(0, Some(numpad))));
+    for i in 1..n {
+        let new_robot = Box::new(KeypadRobot::Direction(DirectionKeypadRobot::new(i, Some(robot))));
+        robot = new_robot
+    }
+
+    // let mut sol_freqs = Vec::new();
+    let mut sum = 0;
+    for button in &code.0 {
+        let paths = robot.press(*button).to_vec();
+        let best = paths
+            .iter()
+            .map(|bp| bp.iter().map(|(k, v)| k.len() * v).sum::<usize>())
+            .min()
+            .unwrap();
+        sum += best;
+    }
+    return sum as i64 * code.num_val();
+}
+
+#[aoc(day21, part1)]
+fn part1(input: &str) -> i64 {
+    let codes = parse(input);
+    codes.iter().map(|c| run_robots(c, 2)).sum::<i64>() as i64
+}
+
+#[aoc(day21, part2)]
+fn part2(input: &str) -> i64 {
+    let codes = parse(input);
+    for i in 0..26 {
+        let res = codes.iter().map(|c| run_robots(c, i)).sum::<i64>() as i64;
+        println!("{i}: {res}");
+    }
+    0
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "029A
+980A
+179A
+456A
+379A";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 126384);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE), 0);
+    }
+}

src/day22.rs

@@ -0,0 +1,155 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+use rustc_hash::FxHashMap;
+
+#[derive(Debug, Eq, PartialEq, PartialOrd, Ord, Clone, Copy)]
+struct Change {
+    price: i8,
+    delta: i8,
+}
+
+type Secret = u64;
+
+fn evolve_secret(mut n: Secret) -> Secret {
+    n = ((n * 64) ^ n) % 16777216;
+    n = ((n / 32) ^ n) % 16777216;
+    n = ((n * 2048) ^ n) % 16777216;
+    n
+}
+
+fn rounds(mut secret: Secret, n: Secret) -> Secret {
+    for _ in 0..n {
+        secret = evolve_secret(secret)
+    }
+    secret
+}
+
+fn prices(mut secret: Secret, n: usize) -> Vec<i8> {
+    let mut prices = vec![(secret % 10) as i8];
+    for _ in 1..n {
+        secret = evolve_secret(secret);
+        prices.push((secret % 10) as i8);
+    }
+    prices
+}
+
+fn build_profit_map(prices: &[i8]) -> FxHashMap<[i8; 4], i8> {
+    let mut profits = FxHashMap::default();
+    let changes = prices
+        .windows(2)
+        .map(|a| Change {
+            price: a[1],
+            delta: a[1] - a[0],
+        })
+        .collect_vec();
+    for i in 3..changes.len() {
+        let seq: [i8; 4] = changes[i - 3..=i]
+            .iter()
+            .map(|c| c.delta)
+            .collect_vec()
+            .try_into()
+            .unwrap();
+        profits.entry(seq).or_insert(changes[i].price);
+    }
+    profits
+}
+
+fn profit_for_sequence(changes: &[FxHashMap<[i8; 4], i8>], seq: &[i8]) -> i64 {
+    changes
+        .iter()
+        .filter_map(|inner| inner.get(seq).map(|v| *v as i64))
+        .sum()
+}
+
+fn find_best_sequence(changes: &[FxHashMap<[i8; 4], i8>]) -> [i8; 4] {
+    let possible_seqs = (0..4).map(|_| (-9..=9i8)).multi_cartesian_product().collect_vec();
+    let (best_seq, _best_profit) = possible_seqs
+        .par_iter()
+        .map_with(changes, |changes, seq| (seq, profit_for_sequence(changes, seq)))
+        .max_by(|(_, a), (_, b)| a.cmp(b))
+        .unwrap();
+
+    best_seq.as_slice().try_into().unwrap()
+}
+
+fn parse(input: &str) -> Vec<Secret> {
+    input.lines().map(|l| l.parse().unwrap()).collect()
+}
+
+#[aoc(day22, part1)]
+pub fn part1(input: &str) -> Secret {
+    let secrets = parse(input);
+
+    secrets.iter().map(|s| rounds(*s, 2000)).sum::<Secret>()
+}
+
+#[aoc(day22, part2)]
+pub fn part2(input: &str) -> i64 {
+    let secrets = parse(input);
+
+    let price_changes = secrets
+        .iter()
+        .map(|s| build_profit_map(&prices(*s, 2000)))
+        .collect_vec();
+
+    let seq = find_best_sequence(&price_changes);
+    profit_for_sequence(&price_changes, &seq)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "1
+10
+100
+2024";
+
+    const EXAMPLE2: &str = "1
+2
+3
+2024";
+
+    #[test]
+    fn evolution() {
+        assert_eq!(evolve_secret(123), 15887950);
+        assert_eq!(evolve_secret(15887950), 16495136);
+        assert_eq!(evolve_secret(16495136), 527345);
+    }
+
+    #[test]
+    fn test_rounds() {
+        assert_eq!(rounds(1, 2000), 8685429);
+        assert_eq!(rounds(10, 2000), 4700978);
+    }
+
+    #[test]
+    fn test_prices() {
+        assert_eq!(prices(123, 10), vec![3, 0, 6, 5, 4, 4, 6, 4, 4, 2]);
+    }
+
+    #[test]
+    fn test_profit() {
+        assert_eq!(
+            profit_for_sequence(&vec![build_profit_map(&prices(123, 10))], &[-1, -1, 0, 2]),
+            6
+        );
+        let secrets = parse(EXAMPLE2);
+
+        let price_changes = secrets
+            .iter()
+            .map(|s| build_profit_map(&prices(*s, 2000)))
+            .collect_vec();
+        assert_eq!(profit_for_sequence(&price_changes, &[-2, 1, -1, 3]), 23);
+    }
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 37327623);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE2), 23);
+    }
+}

src/day23.rs

@@ -0,0 +1,194 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use rustc_hash::{FxHashMap, FxHashSet};
+use std::fmt::{Debug, Display};
+
+#[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
+struct Node([char; 2]);
+
+impl Debug for Node {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_fmt(format_args!("{}", self.0.iter().join("")))
+    }
+}
+
+impl Display for Node {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_fmt(format_args!("{}", self.0.iter().join("")))
+    }
+}
+
+impl From<[char; 2]> for Node {
+    fn from(value: [char; 2]) -> Self {
+        Self(value)
+    }
+}
+
+impl TryFrom<Vec<char>> for Node {
+    type Error = <[char; 2] as TryFrom<Vec<char>>>::Error;
+    fn try_from(value: Vec<char>) -> Result<Self, Self::Error> {
+        let array: [char; 2] = value.try_into()?;
+        Ok(Self(array))
+    }
+}
+
+struct Network {
+    nodes: FxHashSet<Node>,
+    edges: FxHashMap<Node, FxHashSet<Node>>,
+}
+
+impl Network {
+    fn groups_3(&self) -> FxHashSet<Vec<Node>> {
+        let mut sets = FxHashSet::default();
+        for n in &self.nodes {
+            let neighbours = self.edges.get(n).unwrap();
+            for neigh in neighbours {
+                let neighbours2 = self.edges.get(neigh).unwrap();
+                for neigh2 in neighbours2 {
+                    let neighbours3 = self.edges.get(neigh2).unwrap();
+                    if neighbours3.contains(n) {
+                        let mut set = vec![*n, *neigh, *neigh2];
+                        set.sort();
+                        sets.insert(set);
+                    }
+                }
+            }
+        }
+        sets
+    }
+    // Had to study Wikipedia for this one
+    // https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm
+    fn bron_kerbosch(
+        &self,
+        r: FxHashSet<Node>,
+        mut p: FxHashSet<Node>,
+        mut x: FxHashSet<Node>,
+    ) -> Vec<FxHashSet<Node>> {
+        let mut results = Vec::new();
+        if p.is_empty() && x.is_empty() {
+            return vec![r];
+        } else if p.is_empty() {
+            return Vec::new();
+        }
+        // choose the pivot with the most neighbours, to minimize the size of p_iter
+        let p_iter = if let Some(pivot) = p.union(&x).max_by(|a, b| self.edges[a].len().cmp(&self.edges[b].len())) {
+            FxHashSet::from_iter(p.difference(self.edges.get(pivot).unwrap()).copied())
+        } else {
+            p.clone()
+        };
+        for node in &p_iter {
+            let mut new_r = r.clone();
+            new_r.insert(*node);
+
+            let neighbours = FxHashSet::from_iter(self.edges.get(node).unwrap().iter().copied());
+            let new_p = FxHashSet::from_iter(p.intersection(&neighbours).copied());
+            let new_x = FxHashSet::from_iter(x.intersection(&neighbours).copied());
+
+            results.extend(self.bron_kerbosch(new_r, new_p, new_x).into_iter());
+            p.remove(node);
+            x.insert(*node);
+        }
+        results
+    }
+    fn maximal_subgraphs(&self) -> Vec<FxHashSet<Node>> {
+        self.bron_kerbosch(
+            FxHashSet::default(),
+            FxHashSet::from_iter(self.nodes.iter().copied()),
+            FxHashSet::default(),
+        )
+    }
+}
+
+impl From<&str> for Network {
+    fn from(input: &str) -> Self {
+        let mut nodes = FxHashSet::default();
+        let mut edges = FxHashMap::default();
+        for line in input.lines() {
+            let (node1, node2) = line.split_once('-').unwrap();
+            let (node1, node2): (Node, Node) = (
+                node1.chars().collect_vec().try_into().unwrap(),
+                node2.chars().collect_vec().try_into().unwrap(),
+            );
+            if !nodes.contains(&node1) {
+                nodes.insert(node1);
+            }
+            if !nodes.contains(&node2) {
+                nodes.insert(node2);
+            }
+            edges.entry(node1).or_insert(FxHashSet::default()).insert(node2);
+            edges.entry(node2).or_insert(FxHashSet::default()).insert(node1);
+        }
+        Self { nodes, edges }
+    }
+}
+
+fn parse(input: &str) -> Network {
+    input.into()
+}
+
+#[aoc(day23, part1)]
+pub fn part1(input: &str) -> i64 {
+    let network = parse(input);
+
+    let sets = network.groups_3();
+    let t_count = sets.iter().filter(|set| set.iter().any(|s| s.0[0] == 't')).count();
+
+    t_count as i64
+}
+
+#[aoc(day23, part2)]
+pub fn part2(input: &str) -> String {
+    let network = parse(input);
+    let best_sets = network.maximal_subgraphs();
+    let largest_set = best_sets.iter().max_by(|a, b| a.len().cmp(&b.len())).unwrap();
+    let mut largest = largest_set.iter().collect_vec();
+    largest.sort();
+    largest.iter().join(",")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "kh-tc
+qp-kh
+de-cg
+ka-co
+yn-aq
+qp-ub
+cg-tb
+vc-aq
+tb-ka
+wh-tc
+yn-cg
+kh-ub
+ta-co
+de-co
+tc-td
+tb-wq
+wh-td
+ta-ka
+td-qp
+aq-cg
+wq-ub
+ub-vc
+de-ta
+wq-aq
+wq-vc
+wh-yn
+ka-de
+kh-ta
+co-tc
+wh-qp
+tb-vc
+td-yn";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 7);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE), "co,de,ka,ta");
+    }
+}

src/day24.rs

@@ -0,0 +1,229 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+use nom::And;
+use regex::Regex;
+use rustc_hash::FxHashMap;
+
+#[derive(Copy, Clone, Debug)]
+enum Op {
+    And,
+    Or,
+    Xor,
+    Constant,
+}
+
+impl From<&str> for Op {
+    fn from(value: &str) -> Self {
+        match value {
+            "AND" => Self::And,
+            "OR" => Self::Or,
+            "XOR" => Self::Xor,
+            s => panic!("invalid operation {}", s),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+struct Gate {
+    op: Op,
+    value: Option<bool>,
+    arguments: [String; 2],
+}
+
+impl Gate {
+    fn eval(&self, machine: &GateMachine) -> bool {
+        match self.op {
+            Op::And => machine.val_of(&self.arguments[0]) && machine.val_of(&self.arguments[1]),
+            Op::Or => machine.val_of(&self.arguments[0]) || machine.val_of(&self.arguments[1]),
+            Op::Xor => machine.val_of(&self.arguments[0]) ^ machine.val_of(&self.arguments[1]),
+            Op::Constant => self.value.unwrap(),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct GateMachine {
+    gates: FxHashMap<String, Gate>,
+}
+
+impl GateMachine {
+    fn val_of(&self, gate: &str) -> bool {
+        println!("gate: {}", gate);
+        if let Some(val) = self.gates[gate].value {
+            val
+        } else {
+            self.gates[gate].eval(self)
+        }
+    }
+}
+
+fn parse(input: &str) -> GateMachine {
+    let mut gates = FxHashMap::default();
+    for line in input.lines() {
+        println!("{line}");
+        let const_re = Regex::new(r"^([xyz][0-9]{2}): ([01])$").unwrap();
+        let gate_re = Regex::new(r"^([a-z0-9]{3}) (AND|XOR|OR) ([a-z0-9]{3}) -> ([a-z0-9]{3})$").unwrap();
+
+        if let Some(caps) = const_re.captures(line) {
+            println!(" is const: {:?}", caps);
+            gates.insert(
+                caps[1].to_string(),
+                Gate {
+                    op: Op::Constant,
+                    value: if &caps[2] == "1" { Some(true) } else { Some(false) },
+                    arguments: [String::new(), String::new()],
+                },
+            );
+        } else if let Some(caps) = gate_re.captures(line) {
+            println!(" is gate: {:?}", caps);
+            gates.insert(
+                caps[4].to_string(),
+                Gate {
+                    op: Op::from(&caps[2]),
+                    value: None,
+                    arguments: [caps[1].to_string(), caps[3].to_string()],
+                },
+            );
+        }
+    }
+    GateMachine { gates }
+}
+
+#[aoc(day24, part1)]
+pub fn part1(input: &str) -> i64 {
+    let machine = parse(input);
+    let z_gates = machine
+        .gates
+        .keys()
+        .filter(|k| k.starts_with('z'))
+        .map(|s| (s, s.split_at(1).1.parse::<usize>().unwrap()));
+    let bit_vals = z_gates
+        .map(|(name, bit)| if machine.val_of(name) { 1 << bit } else { 0 })
+        .fold(0, |accum, val| accum | val);
+    bit_vals
+}
+
+#[aoc(day24, part2)]
+pub fn part2(input: &str) -> i64 {
+    0
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE1: &str = "x00: 1
+x01: 1
+x02: 1
+y00: 0
+y01: 1
+y02: 0
+
+x00 AND y00 -> z00
+x01 XOR y01 -> z01x00: 1
+x01: 0
+x02: 1
+x03: 1
+x04: 0
+y00: 1
+y01: 1
+y02: 1
+y03: 1
+y04: 1
+
+ntg XOR fgs -> mjb
+y02 OR x01 -> tnw
+kwq OR kpj -> z05
+x00 OR x03 -> fst
+tgd XOR rvg -> z01
+vdt OR tnw -> bfw
+bfw AND frj -> z10
+ffh OR nrd -> bqk
+y00 AND y03 -> djm
+y03 OR y00 -> psh
+bqk OR frj -> z08
+tnw OR fst -> frj
+gnj AND tgd -> z11
+bfw XOR mjb -> z00
+x03 OR x00 -> vdt
+gnj AND wpb -> z02
+x04 AND y00 -> kjc
+djm OR pbm -> qhw
+nrd AND vdt -> hwm
+kjc AND fst -> rvg
+y04 OR y02 -> fgs
+y01 AND x02 -> pbm
+ntg OR kjc -> kwq
+psh XOR fgs -> tgd
+qhw XOR tgd -> z09
+pbm OR djm -> kpj
+x03 XOR y03 -> ffh
+x00 XOR y04 -> ntg
+bfw OR bqk -> z06
+nrd XOR fgs -> wpb
+frj XOR qhw -> z04
+bqk OR frj -> z07
+y03 OR x01 -> nrd
+hwm AND bqk -> z03
+tgd XOR rvg -> z12
+tnw OR pbm -> gnj
+x02 OR y02 -> z02";
+
+    const EXAMPLE2: &str = "x00: 1
+x01: 0
+x02: 1
+x03: 1
+x04: 0
+y00: 1
+y01: 1
+y02: 1
+y03: 1
+y04: 1
+
+ntg XOR fgs -> mjb
+y02 OR x01 -> tnw
+kwq OR kpj -> z05
+x00 OR x03 -> fst
+tgd XOR rvg -> z01
+vdt OR tnw -> bfw
+bfw AND frj -> z10
+ffh OR nrd -> bqk
+y00 AND y03 -> djm
+y03 OR y00 -> psh
+bqk OR frj -> z08
+tnw OR fst -> frj
+gnj AND tgd -> z11
+bfw XOR mjb -> z00
+x03 OR x00 -> vdt
+gnj AND wpb -> z02
+x04 AND y00 -> kjc
+djm OR pbm -> qhw
+nrd AND vdt -> hwm
+kjc AND fst -> rvg
+y04 OR y02 -> fgs
+y01 AND x02 -> pbm
+ntg OR kjc -> kwq
+psh XOR fgs -> tgd
+qhw XOR tgd -> z09
+pbm OR djm -> kpj
+x03 XOR y03 -> ffh
+x00 XOR y04 -> ntg
+bfw OR bqk -> z06
+nrd XOR fgs -> wpb
+frj XOR qhw -> z04
+bqk OR frj -> z07
+y03 OR x01 -> nrd
+hwm AND bqk -> z03
+tgd XOR rvg -> z12
+tnw OR pbm -> gnj";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE1), 4);
+        assert_eq!(part1(EXAMPLE2), 2024);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(EXAMPLE1), 0);
+    }
+}

src/day25.rs

@@ -0,0 +1,143 @@
+use aoc_runner_derive::aoc;
+use itertools::Itertools;
+
+enum LockKey {
+    Lock,
+    Key,
+}
+
+#[derive(Clone, Debug)]
+struct LockPile {
+    keys: Vec<Vec<usize>>,
+    locks: Vec<Vec<usize>>,
+}
+
+fn parse_grid(lines: &Vec<&str>) -> (LockKey, Vec<usize>) {
+    assert_eq!(lines.len(), 7);
+    if lines[0].chars().all(|c| c == '#') {
+        // lock
+        let mut pins = vec![0; 5];
+        for row in 1..lines.len() {
+            let row_s = lines[row];
+            for i in 0..row_s.len() {
+                if row_s.chars().nth(i) == Some('#') {
+                    pins[i] = row
+                }
+            }
+        }
+        (LockKey::Lock, pins)
+    } else if lines[6].chars().all(|c| c == '#') {
+        // key
+        let mut pins = vec![5; 5];
+        for row in (1..lines.len()).rev() {
+            let row_s = lines[row];
+            for i in 0..row_s.len() {
+                if row_s.chars().nth(i) == Some('#') {
+                    pins[i] = 6 - row
+                }
+            }
+        }
+        (LockKey::Key, pins)
+    } else {
+        panic!("not a lock or a key: {:?}", lines);
+    }
+}
+
+fn parse(input: &str) -> LockPile {
+    let mut locks = Vec::new();
+    let mut keys = Vec::new();
+    let mut accum: Vec<&str> = Vec::new();
+    for line in input.lines() {
+        if line == "" {
+            let (lk, pins) = parse_grid(&accum);
+            match lk {
+                LockKey::Lock => locks.push(pins),
+                LockKey::Key => keys.push(pins),
+            }
+            accum.clear();
+        } else {
+            accum.push(line);
+        }
+    }
+    if accum.len() != 0 {
+        let (lk, pins) = parse_grid(&accum);
+        match lk {
+            LockKey::Lock => locks.push(pins),
+            LockKey::Key => keys.push(pins),
+        }
+    }
+    LockPile { keys, locks }
+}
+
+fn test_lock_key(lock: &Vec<usize>, key: &Vec<usize>) -> bool {
+    !lock.iter().zip(key.iter()).any(|(lp, kp)| lp + kp > 5)
+}
+
+#[aoc(day25, part1)]
+pub fn part1(input: &str) -> i64 {
+    let lockpile = parse(input);
+
+    lockpile
+        .locks
+        .iter()
+        .cartesian_product(lockpile.keys.iter())
+        .filter(|(l, k)| test_lock_key(l, k))
+        .count() as i64
+}
+
+#[aoc(day25, part2)]
+pub fn part2(_input: &str) -> String {
+    "run the other solutions for day 25 part 2!".to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    const EXAMPLE: &str = "#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(EXAMPLE), 3);
+    }
+
+    #[test]
+    fn part2_example() {}
+}

src/day3.rs

@@ -0,0 +1,64 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use atoi::FromRadix10;
+use regex::bytes::Regex;
+use std::io::BufRead;
+
+#[aoc_generator(day3)]
+pub fn get_input(input: &[u8]) -> Vec<String> {
+    input.lines().map(|l| l.unwrap()).collect()
+}
+
+// PROBLEM 1 solution
+#[aoc(day3, part1)]
+pub fn part1(input: &[String]) -> u64 {
+    let re = Regex::new(r"(?-u)mul\((\d+),(\d+)\)").unwrap();
+    input
+        .iter()
+        .map(|line| {
+            re.captures_iter(line.as_bytes())
+                .map(|m| u64::from_radix_10(&m[1]).0 * u64::from_radix_10(&m[2]).0)
+                .sum::<u64>()
+        })
+        .sum()
+}
+
+// PROBLEM 2 solution
+#[aoc(day3, part2)]
+pub fn part2(input: &[String]) -> u64 {
+    let mut sum = 0u64;
+    let mut do_mul: u64 = 1;
+    let re = Regex::new(r"(?-u)(do\(\)|don't\(\)|mul\((\d+),(\d+)\))").unwrap();
+    for line in input {
+        let line = line.as_bytes();
+        for m in re.captures_iter(line) {
+            match &m[1] {
+                b"do()" => do_mul = 1,
+                b"don't()" => do_mul = 0,
+                _ => {
+                    sum += u64::from_radix_10(&m[2]).0 * u64::from_radix_10(&m[3]).0 * do_mul;
+                }
+            }
+        }
+    }
+    sum
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day3::*;
+
+    const EXAMPLE1: &[u8] = b"xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))";
+    const EXAMPLE2: &[u8] = b"xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))";
+
+    #[test]
+    fn part1_example() {
+        let input = get_input(EXAMPLE1);
+        assert_eq!(part1(&input), 161);
+    }
+
+    #[test]
+    fn part2_example() {
+        let input = get_input(EXAMPLE2);
+        assert_eq!(part2(&input), 48);
+    }
+}

src/day4.rs

@@ -1,40 +1,12 @@
-use std::fs::File;
-use std::io::{BufRead, BufReader, Lines};
-use std::time::{Duration, Instant};
+use aoc_runner_derive::{aoc, aoc_generator};
+use std::io::{BufRead, Lines};
 
-// BOILERPLATE
-type InputIter = Lines<BufReader<File>>;
-
-pub fn get_input() -> InputIter {
-    let f = File::open("input").unwrap();
-    let br = BufReader::new(f);
-    br.lines()
+#[aoc_generator(day4)]
+pub fn get_input(input: &[u8]) -> WordSearch {
+    WordSearch::from(input.lines())
 }
 
-fn duration_format(duration: Duration) -> String {
-    match duration.as_secs_f64() {
-        x if x > 1.0 => format!("{:.3}s", x),
-        x if x > 0.010 => format!("{:.3}ms", x * 1e3),
-        x => format!("{:.3}us", x * 1e6),
-    }
-}
-
-fn main() {
-    let input = get_input();
-    let start = Instant::now();
-    let ans1 = problem1(input);
-    let duration1 = start.elapsed();
-    println!("Problem 1 solution: {} [{}]", ans1, duration_format(duration1));
-
-    let input = get_input();
-    let start = Instant::now();
-    let ans2 = problem2(input);
-    let duration2 = start.elapsed();
-    println!("Problem 2 solution: {} [{}]", ans2, duration_format(duration2));
-    println!("Total duration: {}", duration_format(duration1 + duration2));
-}
-
-struct WordSearch {
+pub struct WordSearch {
     rows: Vec<String>,
 }
 
@@ -81,22 +53,18 @@ impl WordSearch {
         for x in 0..width {
             for y in 0..height {
                 // check down-right
-                if x <= width - needle.len() && y <= height - needle.len() {
-                    if (0..needle.len())
-                        .into_iter()
-                        .all(|i| self.get(x + i, y + i) == needle.as_bytes()[i].into())
-                    {
-                        count += 1
-                    }
+                if x <= width - needle.len()
+                    && y <= height - needle.len()
+                    && (0..needle.len()).all(|i| self.get(x + i, y + i) == needle.as_bytes()[i].into())
+                {
+                    count += 1
                 }
                 // check down-left
-                if x >= needle.len() - 1 && y <= height - needle.len() {
-                    if (0..needle.len())
-                        .into_iter()
-                        .all(|i| self.get(x - i, y + i) == needle.as_bytes()[i].into())
-                    {
-                        count += 1
-                    }
+                if x >= needle.len() - 1
+                    && y <= height - needle.len()
+                    && (0..needle.len()).all(|i| self.get(x - i, y + i) == needle.as_bytes()[i].into())
+                {
+                    count += 1
                 }
             }
         }
@@ -138,11 +106,10 @@ impl WordSearch {
 }
 
 // PROBLEM 1 solution
-
-fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
+#[aoc(day4, part1)]
+pub fn part1(ws: &WordSearch) -> u64 {
     let needle = "XMAS";
     let needle_rev: String = needle.chars().rev().collect();
-    let ws = WordSearch::from(input);
     ws.count_forward(needle)
         + ws.count_forward(&needle_rev)
         + ws.count_vertical(needle)
@@ -152,17 +119,16 @@ fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
 }
 
 // PROBLEM 2 solution
-fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
-    let ws = WordSearch::from(input);
+#[aoc(day4, part2)]
+pub fn part2(ws: &WordSearch) -> u64 {
     ws.count_x_mas()
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::*;
-    use std::io::Cursor;
+    use crate::day4::*;
 
-    const EXAMPLE: &str = &"MMMSXXMASM
+    const EXAMPLE: &[u8] = b"MMMSXXMASM
 MSAMXMSMSA
 AMXSXMAAMM
 MSAMASMSMX
@@ -174,14 +140,12 @@ MAMMMXMMMM
 MXMXAXMASX";
 
     #[test]
-    fn problem1_example() {
-        let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem1(c.lines()), 18);
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 18);
     }
 
     #[test]
-    fn problem2_example() {
-        let c = Cursor::new(EXAMPLE);
-        assert_eq!(problem2(c.lines()), 9);
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 9);
     }
 }

src/day5.rs

@@ -0,0 +1,148 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use rustc_hash::FxHashMap;
+use std::cmp::Ordering;
+use std::fmt::Debug;
+use std::io::BufRead;
+
+type HashMap<K, V> = FxHashMap<K, V>;
+
+#[aoc_generator(day5)]
+pub fn get_input(input: &[u8]) -> (OrderingRules, Vec<Vec<u64>>) {
+    let mut lines = input.lines();
+
+    let pairs = HashMap::from_iter(
+        lines
+            .by_ref()
+            .map_while(|l| match l {
+                Ok(line) if !line.is_empty() => {
+                    let rule = BeforeRule::from(line);
+                    Some(vec![
+                        ((rule.a, rule.b), Ordering::Less),
+                        ((rule.b, rule.a), Ordering::Greater),
+                    ])
+                }
+                _ => None,
+            })
+            .flatten(),
+    );
+    let updates: Vec<Vec<u64>> = lines
+        .by_ref()
+        .map(|l| l.unwrap().split(',').map(|n| n.parse::<u64>().unwrap()).collect())
+        .collect();
+    (OrderingRules { pairs }, updates)
+}
+
+#[derive(Debug)]
+struct BeforeRule {
+    a: u64,
+    b: u64,
+}
+
+impl From<String> for BeforeRule {
+    fn from(line: String) -> BeforeRule {
+        let nums = line.split_once('|').unwrap();
+        BeforeRule {
+            a: nums.0.parse().unwrap(),
+            b: nums.1.parse().unwrap(),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct OrderingRules {
+    pairs: HashMap<(u64, u64), Ordering>,
+}
+
+impl OrderingRules {
+    fn check(&self, pages: &[u64]) -> bool {
+        pages.is_sorted_by(|a, b| self.is_sorted(*a, *b))
+    }
+    fn cmp(&self, a: u64, b: u64) -> Ordering {
+        if let Some(ord) = self.pairs.get(&(a, b)) {
+            *ord
+        } else {
+            Ordering::Equal
+        }
+    }
+    fn is_sorted(&self, a: u64, b: u64) -> bool {
+        matches!(self.pairs.get(&(a, b)), Some(Ordering::Less) | Some(Ordering::Equal))
+    }
+}
+
+// impl<'a, T: Iterator<Item = &'a str>> From<&mut T> for OrderingRules {
+//     fn from(input: &mut T) -> Self {
+//         let mut rules = Vec::new();
+//         for line in input {
+//             rules.push(line.into())
+//         }
+//         Self { rules }
+//     }
+// }
+
+// PROBLEM 1 solution
+#[aoc(day5, part1)]
+pub fn part1((rules, updates): &(OrderingRules, Vec<Vec<u64>>)) -> u64 {
+    updates
+        .iter()
+        .filter(|update| rules.check(update))
+        .map(|update| update[update.len() / 2])
+        .sum()
+}
+
+// PROBLEM 2 solution
+#[aoc(day5, part2)]
+pub fn part2((rules, updates): &(OrderingRules, Vec<Vec<u64>>)) -> u64 {
+    let mut updates = updates.clone();
+    updates
+        .iter_mut()
+        .filter(|update| !rules.check(update))
+        .map(|update| {
+            update.sort_by(|a, b| rules.cmp(*a, *b));
+            update[update.len() / 2]
+        })
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day5::*;
+
+    const EXAMPLE: &[u8] = b"47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 143);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 123);
+    }
+}

src/day6.rs

@@ -0,0 +1,215 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use bitflags::bitflags;
+use rayon::iter::ParallelIterator;
+use rayon::slice::ParallelSlice;
+use std::fmt;
+use std::io::BufRead;
+use std::ops::BitAnd;
+
+use grid::Grid;
+
+#[aoc_generator(day6)]
+pub fn get_input(input: &[u8]) -> Map {
+    Map::from(input)
+}
+
+#[repr(u8)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
+enum FacingDirection {
+    Up = 1,
+    Down = 2,
+    Left = 4,
+    Right = 8,
+}
+
+impl FacingDirection {
+    fn next(&self) -> FacingDirection {
+        match self {
+            FacingDirection::Up => FacingDirection::Right,
+            FacingDirection::Down => FacingDirection::Left,
+            FacingDirection::Left => FacingDirection::Up,
+            FacingDirection::Right => FacingDirection::Down,
+        }
+    }
+    fn pos_ofs(&self, pos: (i64, i64)) -> (i64, i64) {
+        match self {
+            FacingDirection::Up => (pos.0, pos.1 + -1),
+            FacingDirection::Down => (pos.0, pos.1 + 1),
+            FacingDirection::Left => (pos.0 + -1, pos.1),
+            FacingDirection::Right => (pos.0 + 1, pos.1),
+        }
+    }
+}
+
+enum StepOutcome {
+    LeftMap,
+    LoopFound,
+    Continue,
+}
+
+#[derive(Eq, PartialEq)]
+enum RunOutcome {
+    LeftMap,
+    LoopFound,
+}
+
+bitflags! {
+    #[derive(Copy, Clone, Eq, PartialEq, Debug)]
+    pub struct DirectionSet: u8 {
+        const Up = 1;
+        const Down = 2;
+        const Left = 4;
+        const Right = 8;
+    }
+}
+
+impl From<FacingDirection> for DirectionSet {
+    fn from(value: FacingDirection) -> Self {
+        match value {
+            FacingDirection::Up => DirectionSet::Up,
+            FacingDirection::Down => DirectionSet::Down,
+            FacingDirection::Left => DirectionSet::Left,
+            FacingDirection::Right => DirectionSet::Right,
+        }
+    }
+}
+
+impl fmt::Display for DirectionSet {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl BitAnd<FacingDirection> for DirectionSet {
+    type Output = DirectionSet;
+    fn bitand(self, rhs: FacingDirection) -> Self::Output {
+        self & DirectionSet::from(rhs)
+    }
+}
+
+#[derive(Clone)]
+pub struct Map {
+    grid: Grid<u8>,
+    visited_from: Grid<DirectionSet>,
+    guard_facing: FacingDirection,
+    guard_pos: (i64, i64),
+    path: Vec<((i64, i64), FacingDirection)>,
+}
+
+impl<T: BufRead> From<T> for Map {
+    fn from(input: T) -> Self {
+        let grid = Grid::from(input);
+        let visited_from = grid.same_shape(DirectionSet::empty());
+        let guard_pos = grid.find(&b'^').expect("Guard not found");
+        let guard_facing = FacingDirection::Up;
+        Self {
+            grid,
+            guard_pos: guard_pos.into(),
+            guard_facing,
+            visited_from,
+            path: Vec::new(),
+        }
+    }
+}
+
+impl Map {
+    fn look(&self, dir: &FacingDirection) -> Option<&u8> {
+        self.grid.get(&dir.pos_ofs(self.guard_pos))
+    }
+    /// Move one step in the facing direction, return if we are still inside the bounds
+    fn step_guard<const RECORD_PATH: bool>(&mut self) -> StepOutcome {
+        let new_pos = self.guard_facing.pos_ofs(self.guard_pos);
+        if self
+            .visited_from
+            .get(&new_pos)
+            .is_some_and(|dirs| dirs.contains(self.guard_facing.into()))
+        {
+            StepOutcome::LoopFound
+        } else if self.grid.set(&new_pos, b'X').is_some() {
+            if RECORD_PATH {
+                self.path.push((new_pos, self.guard_facing));
+            }
+            self.visited_from.set(
+                &new_pos,
+                *self.visited_from.get(&new_pos).unwrap() | self.guard_facing.into(),
+            );
+            self.guard_pos = new_pos;
+            StepOutcome::Continue
+        } else {
+            StepOutcome::LeftMap
+        }
+    }
+    fn run_guard<const RECORD_PATH: bool>(&mut self) -> RunOutcome {
+        while let Some(val) = self.look(&self.guard_facing) {
+            match val {
+                b'#' => {
+                    // obstacle, turn right
+                    self.guard_facing = self.guard_facing.next();
+                }
+                _ => match self.step_guard::<RECORD_PATH>() {
+                    StepOutcome::LeftMap => return RunOutcome::LeftMap,
+                    StepOutcome::LoopFound => return RunOutcome::LoopFound,
+                    StepOutcome::Continue => {}
+                },
+            }
+        }
+        RunOutcome::LeftMap
+    }
+}
+
+// PROBLEM 1 solution
+#[aoc(day6, part1)]
+pub fn part1(map: &Map) -> u64 {
+    let mut map = map.clone();
+    map.run_guard::<false>();
+
+    map.grid.count(&b'X') as u64
+}
+
+// PROBLEM 2 solution
+#[aoc(day6, part2)]
+pub fn part2(input_map: &Map) -> u64 {
+    // Use the solution from problem 1 to reduce the number of positions where obstacle placement will change the path
+    let mut path_map = input_map.clone();
+    path_map.run_guard::<true>();
+
+    path_map
+        .path
+        .par_windows(2)
+        .filter(|prev_cur| {
+            let last_posdir = prev_cur[0];
+            let mut test_map = input_map.clone();
+            test_map.grid.set(&prev_cur[1].0, b'#').unwrap();
+            test_map.guard_pos = last_posdir.0;
+            test_map.guard_facing = last_posdir.1;
+
+            test_map.run_guard::<false>() == RunOutcome::LoopFound
+        })
+        .count() as u64
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day6::*;
+
+    const EXAMPLE: &[u8] = b"....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 41);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 6);
+    }
+}

src/day7.rs

@@ -0,0 +1,121 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+use std::io::{BufRead, Lines};
+
+#[aoc_generator(day7)]
+pub fn get_input(input: &[u8]) -> Calibrations {
+    Calibrations::from(input.lines())
+}
+
+#[derive(Debug, Clone)]
+struct Calibration {
+    result: u64,
+    numbers: Vec<u64>,
+}
+
+impl From<&str> for Calibration {
+    fn from(value: &str) -> Self {
+        let (result, rest) = value.split_once(':').unwrap();
+        Self {
+            result: result.parse().unwrap(),
+            numbers: rest.split_ascii_whitespace().map(|s| s.parse().unwrap()).collect(),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Calibrations {
+    cals: Vec<Calibration>,
+}
+
+#[derive(Debug, Copy, Clone)]
+enum Operator {
+    Add,
+    Multiply,
+    Concatenate,
+}
+
+impl Operator {
+    fn exec(&self, a: u64, b: u64) -> u64 {
+        match self {
+            Operator::Add => a + b,
+            Operator::Multiply => a * b,
+            Operator::Concatenate => u64::pow(10, b.ilog10() + 1) * a + b,
+        }
+    }
+}
+
+impl<T: BufRead> From<Lines<T>> for Calibrations {
+    fn from(input: Lines<T>) -> Self {
+        let cals = input.map(|l| l.unwrap().as_str().into()).collect();
+        Self { cals }
+    }
+}
+
+impl Calibrations {
+    fn possible(&self, operators: &[Operator]) -> u64 {
+        self.cals
+            .par_iter()
+            .map(|cal| eval_calibration(operators, cal.result, cal.numbers[0], &cal.numbers[1..]))
+            .map(|result| result.unwrap_or(0))
+            .sum()
+    }
+}
+
+fn eval_calibration(operators: &[Operator], expect: u64, left: u64, right: &[u64]) -> Option<u64> {
+    if left > expect {
+        // all operations make the number larger, so this branch is hopeless, early exit
+        return None;
+    }
+    if right.is_empty() {
+        // base case - no further operations
+        if left == expect {
+            return Some(left);
+        } else {
+            return None;
+        }
+    }
+    operators
+        .iter()
+        .map(|oper| eval_calibration(operators, expect, oper.exec(left, right[0]), &right[1..]))
+        .find_map(|result| result)
+}
+
+// PROBLEM 1 solution
+#[aoc(day7, part1)]
+pub fn part1(cals: &Calibrations) -> u64 {
+    let operators = [Operator::Multiply, Operator::Add];
+    cals.possible(&operators)
+}
+
+// PROBLEM 2 solution
+#[aoc(day7, part2)]
+pub fn part2(cals: &Calibrations) -> u64 {
+    let operators = [Operator::Multiply, Operator::Add, Operator::Concatenate];
+    cals.possible(&operators)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day7::*;
+
+    const EXAMPLE: &[u8] = b"190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 3749);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 11387);
+    }
+}

src/day8.rs

@@ -0,0 +1,99 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use grid::Grid;
+use itertools::Itertools;
+use rustc_hash::FxHashSet;
+use std::io::BufRead;
+
+type HashSet<T> = FxHashSet<T>;
+
+#[aoc_generator(day8)]
+pub fn get_input(input: &[u8]) -> AntennaMap {
+    AntennaMap::from(input)
+}
+
+pub struct AntennaMap {
+    map: Grid<u8>,
+}
+
+impl<T: BufRead> From<T> for AntennaMap {
+    fn from(input: T) -> Self {
+        Self { map: Grid::from(input) }
+    }
+}
+
+impl AntennaMap {
+    fn find_antinodes(&self, start: usize, reps: Option<usize>) -> Grid<bool> {
+        let mut antinodes = Grid::with_shape(self.map.width(), self.map.height(), false);
+        // find the unique frequencies in a dumb way
+        // NOTE: The dumb way is faster than the slightly-smarter ways I tried
+        let freq_set: HashSet<&u8> = HashSet::from_iter(self.map.data.iter().filter(|c| **c != b'.'));
+
+        // for each unique frequency, get all the pairs' positions
+        for freq in freq_set {
+            for pair in self
+                .map
+                .data
+                .iter()
+                .enumerate()
+                .filter(|(_, c)| *c == freq)
+                .map(|(i, _)| self.map.coord(i as i64).unwrap())
+                .permutations(2)
+            {
+                // permutations generates both pairs, ie. ((1,2),(2,1)) and ((2,1),(1,2)) so we don't need
+                // to consider the 'negative' side of the line, which will be generated by the other pair
+                let (a, b) = (pair[0], pair[1]);
+                let offset = (a.x - b.x, a.y - b.y);
+                for i in (start..).map_while(|i| if Some(i - start) != reps { Some(i as i64) } else { None }) {
+                    let node_pos = (a.x + i * offset.0, a.y + i * offset.1);
+                    if antinodes.set(&node_pos, true).is_none() {
+                        // left the grid
+                        break;
+                    }
+                }
+            }
+        }
+        antinodes
+    }
+}
+
+// PROBLEM 1 solution
+#[aoc(day8, part1)]
+pub fn part1(map: &AntennaMap) -> u64 {
+    let antinodes = map.find_antinodes(1, Some(1));
+    antinodes.count(&true) as u64
+}
+
+// PROBLEM 2 solution
+#[aoc(day8, part2)]
+pub fn part2(map: &AntennaMap) -> u64 {
+    let antinodes = map.find_antinodes(0, None);
+    antinodes.count(&true) as u64
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day8::*;
+
+    const EXAMPLE: &[u8] = b"............
+........0...
+.....0......
+.......0....
+....0.......
+......A.....
+............
+............
+........A...
+.........A..
+............
+............";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 14);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 34);
+    }
+}

src/day9.rs

@@ -0,0 +1,166 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+use itertools::Itertools;
+use std::fmt::{Display, Write};
+use std::io::{BufRead, Lines};
+
+#[aoc_generator(day9)]
+pub fn get_input(input: &[u8]) -> DiskMap {
+    DiskMap::from(input.lines())
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Copy)]
+enum Unit {
+    File(usize),
+    Free,
+}
+
+#[derive(Clone)]
+struct Inode {
+    id: usize,
+    pos: usize,
+    len: u8,
+}
+
+#[derive(Clone)]
+pub struct DiskMap {
+    map: Vec<Unit>,
+    files: Vec<Inode>,
+    frees: Vec<Inode>,
+}
+
+impl<T: BufRead> From<Lines<T>> for DiskMap {
+    fn from(mut input: Lines<T>) -> Self {
+        let line_s = input.next().unwrap().unwrap();
+        let line = line_s.as_bytes();
+        let mut file_id = 0;
+        let mut map = Vec::new();
+        let mut files = Vec::new();
+        let mut frees = Vec::new();
+        for (i, c) in line.iter().enumerate() {
+            let len = c - b'0';
+            if i % 2 == 0 {
+                // file
+                files.push(Inode {
+                    id: file_id,
+                    pos: map.len(),
+                    len,
+                });
+                for _ in 0..len {
+                    map.push(Unit::File(file_id))
+                }
+                file_id += 1;
+            } else {
+                // free
+                frees.push(Inode {
+                    id: 0,
+                    pos: map.len(),
+                    len,
+                });
+                for _ in 0..len {
+                    map.push(Unit::Free)
+                }
+            }
+        }
+        Self { map, files, frees }
+    }
+}
+
+impl Display for DiskMap {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for unit in &self.map {
+            match unit {
+                Unit::File(i) => f.write_char((b'0' + (*i % 10) as u8) as char)?,
+                Unit::Free => f.write_char('.')?,
+            }
+        }
+        Ok(())
+    }
+}
+
+impl DiskMap {
+    fn checksum(&self) -> u64 {
+        self.map
+            .iter()
+            .enumerate()
+            .map(|(i, u)| match u {
+                Unit::File(id) => i * id,
+                Unit::Free => 0,
+            })
+            .sum::<usize>() as u64
+    }
+}
+
+// PROBLEM 1 solution
+#[aoc(day9, part1)]
+pub fn part1(map: &DiskMap) -> u64 {
+    let mut map = map.to_owned();
+    let mut last_free = 0;
+    for file in map.files.iter().rev() {
+        let frees = map
+            .map
+            .iter()
+            .enumerate()
+            .skip(last_free) // we greedy fill, so no need to check for free space before the last one we used
+            .take(file.pos + file.len as usize) // and we only need to search until the end of the current file
+            .filter(|(_i, u)| **u == Unit::Free || **u == Unit::File(file.id)) // look for free space or our existing space
+            .map(|(i, _u)| i)
+            .take(file.len as usize) // get the first file.len free blocks
+            .collect_vec();
+        // Note: no need to test for too small frees list here, since we are guaranteed at worst to find our current position
+        if frees[0] >= file.pos {
+            // if the first available free is > file.pos, it's fully packed, job done
+            break;
+        }
+        #[allow(clippy::needless_range_loop)]
+        for j in 0..file.len as usize {
+            map.map.swap(frees[j], file.pos + j);
+        }
+        last_free = frees[file.len as usize - 1]
+    }
+    map.checksum()
+}
+
+// PROBLEM 2 solution
+#[aoc(day9, part2)]
+pub fn part2(map: &DiskMap) -> u64 {
+    let mut map = map.to_owned();
+    for file in map.files.iter().rev() {
+        let free = map.frees.iter_mut().find(|inode| inode.len >= file.len); // find the first entry in the free space map large enough
+        if let Some(free) = free {
+            if free.pos >= file.pos {
+                // if it's past our position, continue, but can't break since there might be free space for future files
+                continue;
+            }
+            for j in 0..file.len {
+                map.map.swap(free.pos + j as usize, file.pos + j as usize);
+            }
+            // Note: It is slightly faster to keep these hanging around in the free map with size = 0 then to remove them from the vec
+            free.len -= file.len;
+            free.pos += file.len as usize;
+
+            map.frees.push(Inode {
+                id: 0,
+                pos: file.pos,
+                len: file.len,
+            });
+        }
+    }
+    map.checksum()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::day9::*;
+
+    const EXAMPLE: &[u8] = b"2333133121414131402";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&get_input(EXAMPLE)), 1928);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&get_input(EXAMPLE)), 2858);
+    }
+}

src/lib.rs

@@ -0,0 +1,28 @@
+pub mod day1;
+pub mod day10;
+pub mod day11;
+pub mod day12;
+pub mod day13;
+pub mod day14;
+pub mod day15;
+pub mod day16;
+pub mod day17;
+pub mod day18;
+pub mod day19;
+pub mod day2;
+pub mod day20;
+pub mod day21;
+pub mod day22;
+pub mod day23;
+pub mod day24;
+pub mod day25;
+pub mod day3;
+pub mod day4;
+pub mod day5;
+pub mod day6;
+pub mod day7;
+pub mod day8;
+pub mod day9;
+
+use aoc_runner_derive::aoc_lib;
+aoc_lib! { year = 2024 }

src/main.rs

@@ -0,0 +1,3 @@
+use aoc_runner_derive::aoc_main;
+
+aoc_main! { lib = aoc2024 }

utils/grid/Cargo.lock

@@ -3,5 +3,5 @@
 version = 3
 
 [[package]]
-name = "day1"
+name = "grid"
 version = "0.1.0"

utils/grid/Cargo.toml

@@ -1,6 +1,9 @@
 [package]
-name = "day2"
+name = "grid"
 version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+
+[lib]
+path = "lib.rs"

utils/grid/lib.rs

@@ -0,0 +1,495 @@
+use std::{
+    fmt::{Debug, Display, Formatter, Write},
+    io::{BufRead, Cursor},
+    iter::repeat_n,
+    mem::swap,
+    ops::{Add, AddAssign, Sub},
+    str::FromStr,
+};
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Coord2d {
+    pub x: i64,
+    pub y: i64,
+}
+
+pub trait AsCoord2d {
+    fn to_coord(self) -> Coord2d;
+    fn x(&self) -> i64;
+    fn y(&self) -> i64;
+}
+
+impl<T: AsCoord2d> Sub<T> for &Coord2d {
+    type Output = Coord2d;
+    fn sub(self, rhs: T) -> Self::Output {
+        Coord2d {
+            x: self.x() - rhs.x(),
+            y: self.y() - rhs.y(),
+        }
+    }
+}
+
+impl<T: AsCoord2d> Add<T> for &Coord2d {
+    type Output = Coord2d;
+    fn add(self, rhs: T) -> Self::Output {
+        Coord2d {
+            x: self.x() + rhs.x(),
+            y: self.y() + rhs.y(),
+        }
+    }
+}
+
+impl<T: AsCoord2d> Add<&T> for Coord2d {
+    type Output = Coord2d;
+    fn add(self, rhs: &T) -> Self::Output {
+        Coord2d {
+            x: self.x() + rhs.x(),
+            y: self.y() + rhs.y(),
+        }
+    }
+}
+
+impl AsCoord2d for Coord2d {
+    fn to_coord(self) -> Coord2d {
+        self
+    }
+    fn x(&self) -> i64 {
+        self.x
+    }
+    fn y(&self) -> i64 {
+        self.y
+    }
+}
+
+impl AsCoord2d for &Coord2d {
+    fn to_coord(self) -> Coord2d {
+        self.to_owned()
+    }
+    fn x(&self) -> i64 {
+        self.x
+    }
+    fn y(&self) -> i64 {
+        self.y
+    }
+}
+
+impl<T> AsCoord2d for (T, T)
+where
+    T: Copy + TryInto<i64>,
+    <T as TryInto<i64>>::Error: Debug,
+{
+    fn to_coord(self) -> Coord2d {
+        Coord2d {
+            x: self.0.try_into().unwrap(),
+            y: self.1.try_into().unwrap(),
+        }
+    }
+    fn x(&self) -> i64 {
+        self.0.try_into().unwrap()
+    }
+    fn y(&self) -> i64 {
+        self.1.try_into().unwrap()
+    }
+}
+
+impl<T> AsCoord2d for &(T, T)
+where
+    T: Copy + TryInto<i64>,
+    <T as TryInto<i64>>::Error: Debug,
+{
+    fn to_coord(self) -> Coord2d {
+        Coord2d {
+            x: self.0.try_into().unwrap(),
+            y: self.1.try_into().unwrap(),
+        }
+    }
+    fn x(&self) -> i64 {
+        self.0.try_into().unwrap()
+    }
+    fn y(&self) -> i64 {
+        self.1.try_into().unwrap()
+    }
+}
+
+impl From<Coord2d> for (i64, i64) {
+    fn from(value: Coord2d) -> Self {
+        (value.x, value.y)
+    }
+}
+
+#[derive(Debug)]
+pub struct GridRowIter<'a, T> {
+    iter: std::slice::Iter<'a, T>,
+}
+
+impl<'a, T: Clone + Eq + PartialEq + Debug> GridRowIter<'a, T> {
+    fn new(grid: &'a Grid<T>, y: i64) -> Self {
+        let iter = grid.data[y as usize * grid.width()..(y as usize + 1) * grid.width()].iter();
+        Self { iter }
+    }
+}
+
+impl<'a, T> Iterator for GridRowIter<'a, T> {
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+#[derive(Debug)]
+pub struct GridColIter<'a, T> {
+    grid: &'a Grid<T>,
+    stride: usize,
+    cur: usize,
+}
+
+impl<'a, T: Clone + Eq + PartialEq + Debug> GridColIter<'a, T> {
+    fn new(grid: &'a Grid<T>, x: i64) -> Self {
+        Self {
+            grid,
+            stride: grid.width(),
+            cur: x as usize,
+        }
+    }
+}
+
+impl<'a, T: Clone + Eq + PartialEq + Debug> Iterator for GridColIter<'a, T> {
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        let cur = self.cur;
+        self.cur += self.stride;
+        if cur < self.grid.data.len() {
+            Some(&self.grid.data[cur])
+        } else {
+            None
+        }
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.grid.height() - 1, Some(self.grid.height() - 1))
+    }
+}
+
+#[derive(Clone, Eq, PartialEq, Debug)]
+pub struct Grid<T> {
+    pub data: Vec<T>,
+    width: i64,
+}
+
+impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
+    /// Returns a new [Grid] with the same shape (width x height) as `self`, filled with `fill`
+    pub fn same_shape<NT: Clone + Eq + PartialEq + Debug>(&self, fill: NT) -> Grid<NT> {
+        Grid::with_shape(self.width(), self.height(), fill)
+    }
+    /// Returns a new [Grid] with the given shape (width x height), filled with `fill`
+    pub fn with_shape(width: usize, height: usize, fill: T) -> Self {
+        Self {
+            data: Vec::from_iter(repeat_n(fill, width * height)),
+            width: width as i64,
+        }
+    }
+    pub fn width(&self) -> usize {
+        self.width as usize
+    }
+    pub fn height(&self) -> usize {
+        self.data.len() / self.width()
+    }
+    pub fn pos<C: AsCoord2d>(&self, c: &C) -> i64 {
+        c.y() * self.width + c.x()
+    }
+    pub fn coord(&self, pos: i64) -> Option<Coord2d> {
+        if pos < 0 || pos >= self.data.len() as i64 {
+            None
+        } else {
+            Some(Coord2d {
+                x: pos % self.width,
+                y: pos / self.width,
+            })
+        }
+    }
+    // pub fn coord_iter(&self) -> CoordIter<_> {
+    //     CoordIter { pos: 0, grid: self }
+    // }
+    pub fn is_valid<C: AsCoord2d>(&self, c: &C) -> bool {
+        if c.x() < 0 || c.x() >= self.width {
+            return false;
+        }
+        if c.y() < 0 || c.y() as usize >= self.height() {
+            return false;
+        }
+        return true;
+    }
+    fn valid_pos<C: AsCoord2d>(&self, c: &C) -> Option<usize> {
+        if c.x() < 0 || c.x() >= self.width {
+            return None;
+        }
+        if c.y() < 0 || c.y() as usize >= self.height() {
+            return None;
+        }
+        let pos = self.pos(c);
+        if pos < 0 || pos as usize >= self.data.len() {
+            return None;
+        }
+        self.pos(c).try_into().ok()
+    }
+    pub fn get<C: AsCoord2d>(&self, c: &C) -> Option<&T> {
+        match self.valid_pos(c) {
+            Some(pos) => Some(&self.data[pos]),
+            None => None,
+        }
+    }
+    pub fn get_mut<C: AsCoord2d>(&mut self, c: &C) -> Option<&mut T> {
+        match self.valid_pos(c) {
+            Some(pos) => Some(self.data.get_mut(pos).unwrap()),
+            None => None,
+        }
+    }
+    pub fn set<C: AsCoord2d>(&mut self, c: &C, mut val: T) -> Option<T> {
+        match self.valid_pos(c) {
+            Some(pos) => {
+                swap(&mut self.data[pos], &mut val);
+                Some(val)
+            }
+            None => None,
+        }
+    }
+    pub fn increment<'a, A, C: AsCoord2d>(&'a mut self, c: &C, i: A) -> Option<&'a T>
+    where
+        T: AddAssign<A>,
+    {
+        match self.valid_pos(c) {
+            Some(pos) => {
+                self.data[pos] += i;
+                Some(&self.data[pos])
+            }
+            None => None,
+        }
+    }
+    pub fn row(&self, y: i64) -> Option<&[T]> {
+        if y < self.height() as i64 && y >= 0 {
+            Some(&self.data[self.pos(&(0, y)) as usize..self.pos(&(self.width, y)) as usize])
+        } else {
+            None
+        }
+    }
+
+    pub fn row_iter(&self, y: i64) -> Option<GridRowIter<T>> {
+        if (y as usize) < self.height() {
+            Some(GridRowIter::new(self, y))
+        } else {
+            None
+        }
+    }
+
+    pub fn col(&self, x: i64) -> Option<Vec<&T>> {
+        if let Some(iter) = self.col_iter(x) {
+            Some(iter.collect())
+        } else {
+            None
+        }
+    }
+
+    pub fn col_iter(&self, x: i64) -> Option<GridColIter<T>> {
+        if (x as usize) < self.width() {
+            Some(GridColIter::new(self, x))
+        } else {
+            None
+        }
+    }
+
+    pub fn find(&self, haystack: &T) -> Option<Coord2d> {
+        self.coord(
+            self.data
+                .iter()
+                .enumerate()
+                .find_map(|(pos, val)| if val == haystack { Some(pos as i64) } else { None })
+                .unwrap_or(-1),
+        )
+    }
+    pub fn count(&self, haystack: &T) -> usize {
+        self.data.iter().filter(|item| *item == haystack).count()
+    }
+
+    pub fn forward_slice<C: AsCoord2d>(&self, start: &C, len: i64) -> Option<&[T]> {
+        let pos = (self.valid_pos(start), self.valid_pos(&(start.x() + len - 1, start.y())));
+        match pos {
+            (Some(pos1), Some(pos2)) => Some(&self.data[pos1..pos2 + 1]),
+            _ => None,
+        }
+    }
+
+    pub fn swap<A: AsCoord2d, B: AsCoord2d>(&mut self, a: A, b: B) {
+        if let (Some(a), Some(b)) = (self.valid_pos(&a), self.valid_pos(&b)) {
+            self.data.swap(a, b)
+        }
+    }
+
+    // fn window_compare_impl<const REV: bool>(&self, needle: &[T]) -> Vec<(i64, i64)> {
+    //     if (self.width as usize) < needle.len() {
+    //         return Vec::new();
+    //     }
+    //     let mut res = Vec::new();
+    //     for y in 0..self.height() as i64 {
+    //         let mut windows_tmp = self.row(y).unwrap().windows(needle.len());
+    //         let windows = if REV {
+    //             windows_tmp.rev()
+    //         } else {
+    //             windows_tmp
+    //         };
+
+    //         res.extend(
+    //             windows
+    //                 .enumerate()
+    //                 .filter_map(|(x, w)| if w == needle { Some((x as i64, y)) } else { None }),
+    //         );
+    //     }
+    //     res
+    // }
+}
+
+impl<T: BufRead> From<T> for Grid<u8> {
+    fn from(input: T) -> Grid<u8> {
+        let mut data = Vec::new();
+        let mut width = 0;
+        for line in input.split(b'\n').map(|i| i.unwrap()) {
+            if width == 0 {
+                width = line.len() as i64
+            } else if line.len() as i64 != width {
+                panic!("Grids must have fixed length rows")
+            }
+            data.extend_from_slice(&line);
+        }
+        Grid { data, width }
+    }
+}
+
+// Should be Grid<char>?
+impl FromStr for Grid<u8> {
+    type Err = Box<dyn std::error::Error>;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(Cursor::new(s).into())
+    }
+}
+
+// impl<T: Copy + Eq + PartialEq + Display + Debug + Into<char>> Display for Grid<T> {
+//     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+//         for y in 0..self.height() {
+//             for x in 0..self.width() {
+//                 f.write_fmt(format_args!("{}",self.get(x as i64, y as i64).unwrap() as char))?;
+//             }
+//             f.write_char('\n')?;
+//         }
+//         f.write_char('\n')
+//     }
+// }
+
+impl Display for Grid<u8> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        for y in 0..self.height() {
+            for x in 0..self.width() {
+                f.write_fmt(format_args!("{}", *self.get(&(x as i64, y as i64)).unwrap() as char))?;
+            }
+            f.write_char('\n')?;
+        }
+        f.write_char('\n')
+    }
+}
+
+impl Display for Grid<bool> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        for y in 0..self.height() {
+            for x in 0..self.width() {
+                f.write_fmt(format_args!(
+                    "{}",
+                    match *self.get(&(x as i64, y as i64)).unwrap() {
+                        true => '.',
+                        false => '#',
+                    }
+                ))?;
+            }
+            f.write_char('\n')?;
+        }
+        f.write_char('\n')
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static TEST_VECTOR: &[u8] = b"ABCD
+EFGH
+IJKL
+FBCG";
+
+    static TEST_VECTOR_S: &str = "ABCD
+EFGH
+IJKL
+FBCG";
+
+    fn unchecked_load() -> Grid<u8> {
+        Grid::from(TEST_VECTOR)
+    }
+
+    #[test]
+    fn from_string() {
+        let grid = unchecked_load();
+        assert_eq!(grid.data, "ABCDEFGHIJKLFBCG".as_bytes());
+        assert_eq!(
+            TEST_VECTOR_S.parse::<Grid<u8>>().unwrap().data,
+            "ABCDEFGHIJKLFBCG".as_bytes()
+        );
+    }
+
+    #[test]
+    fn indexing() {
+        let grid = unchecked_load();
+        assert_eq!(grid.get(&(0, 0)), Some(b'A').as_ref());
+        assert_eq!(grid.get(&(3, 3)), Some(b'G').as_ref());
+        assert_eq!(grid.get(&(-1, 0)), None);
+        assert_eq!(grid.get(&(0, -1)), None);
+        assert_eq!(grid.get(&(5, 0)), None);
+        assert_eq!(grid.get(&(0, 5)), None);
+    }
+
+    #[test]
+    fn forward_slice() {
+        let grid = unchecked_load();
+        assert_eq!(grid.forward_slice(&(0, 0), 2), Some(b"AB".as_slice()));
+        assert_eq!(grid.forward_slice(&(2, 0), 2), Some(b"CD".as_slice()));
+        assert_eq!(grid.forward_slice(&(2, 0), 3), None);
+        assert_eq!(grid.forward_slice(&(0, 2), 4), Some(b"IJKL".as_slice()));
+    }
+
+    #[test]
+    fn row_iter() {
+        let grid = unchecked_load();
+        assert_eq!(
+            grid.row_iter(2).unwrap().collect::<Vec<_>>(),
+            [&b'I', &b'J', &b'K', &b'L']
+        );
+        assert!(grid.row_iter(-1).is_none());
+        assert!(grid.row_iter(4).is_none());
+    }
+
+    #[test]
+    fn col_iter() {
+        let grid = unchecked_load();
+        assert_eq!(
+            grid.col_iter(2).unwrap().collect::<Vec<_>>(),
+            [&b'C', &b'G', &b'K', &b'C']
+        );
+        assert!(grid.col_iter(-1).is_none());
+        assert!(grid.col_iter(4).is_none());
+    }
+
+    // #[test]
+    // fn window_compare() {
+    //     let grid = unchecked_load();
+    //     assert_eq!(grid.window_compare(b"IJKL"), &[(0, 2)]);
+    //     assert_eq!(grid.window_compare(b"BC"), &[(1, 0), (1, 3)]);
+    //     assert_eq!(grid.window_compare(b"LF").len(), 0);
+    // }
+}

utils/misc/Cargo.lock

@@ -0,0 +1,25 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "autocfg"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ace50bade8e6234aa140d9a2f552bbee1db4d353f69b8217bc503490fc1a9f26"
+
+[[package]]
+name = "misc"
+version = "0.1.0"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
+dependencies = [
+ "autocfg",
+]

utils/misc/Cargo.toml

@@ -1,6 +1,7 @@
 [package]
-name = "day1"
+name = "misc"
 version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+num-traits = "0.2.19"

utils/misc/src/lib.rs

@@ -0,0 +1,98 @@
+use num_traits::Signed;
+use std::fmt::Display;
+use std::ops::{Add, AddAssign};
+
+/// Wrapped signed integer with custom upper bound with wrapping of 0s to the upper bound
+#[derive(Eq, Clone, Copy)]
+pub struct CustomWrapped<T: Signed + Copy> {
+    pub val: T,
+    pub bound: T,
+}
+
+impl<T: Signed + Copy> Add<T> for CustomWrapped<T> {
+    type Output = CustomWrapped<T>;
+    fn add(self, rhs: T) -> Self::Output {
+        Self {
+            val: ((self.val + rhs % self.bound) + self.bound) % self.bound,
+            bound: self.bound,
+        }
+    }
+}
+
+impl<T: Signed + Copy> Add<T> for &CustomWrapped<T> {
+    type Output = CustomWrapped<T>;
+    fn add(self, rhs: T) -> Self::Output {
+        CustomWrapped {
+            val: ((self.val + rhs % self.bound) + self.bound) % self.bound,
+            bound: self.bound,
+        }
+    }
+}
+
+impl<T: Signed + Copy> AddAssign<T> for CustomWrapped<T> {
+    fn add_assign(&mut self, rhs: T) {
+        self.val = ((self.val + rhs % self.bound) + self.bound) % self.bound
+    }
+}
+
+impl<T: Signed + Copy> CustomWrapped<T> {
+    pub fn new(val: T, bound: T) -> Self {
+        Self { val, bound }
+    }
+}
+
+impl<T: Signed + Copy + PartialEq> PartialEq for CustomWrapped<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.val.eq(&other.val)
+    }
+}
+
+impl<T: Signed + PartialOrd + Copy> PartialOrd for CustomWrapped<T> {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        self.val.partial_cmp(&other.val)
+    }
+}
+
+impl<T: Signed + Ord + Copy> Ord for CustomWrapped<T> {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.val.cmp(&other.val)
+    }
+}
+
+impl<T: Signed + PartialEq + Copy> PartialEq<T> for CustomWrapped<T> {
+    fn eq(&self, other: &T) -> bool {
+        self.val == *other
+    }
+}
+
+impl<T: Signed + PartialOrd + Copy> PartialOrd<T> for CustomWrapped<T> {
+    fn partial_cmp(&self, other: &T) -> Option<std::cmp::Ordering> {
+        self.val.partial_cmp(other)
+    }
+}
+
+impl<T: Display + Signed + Copy> Display for CustomWrapped<T>
+where
+    T: Display,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.val.fmt(f)
+    }
+}
+
+// impl<T> Into<T> for CustomWrapped<T> {
+//     fn into(self) -> T {
+//         self.val
+//     }
+// }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+}