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

@@ -19,6 +19,7 @@ jobs:
         cache: true
         components: clippy, rustfmt
         toolchain: stable
+        rustflags: ""
 
     - name: install cargo-aoc
       run: cargo install --locked cargo-aoc
@@ -48,16 +49,14 @@ jobs:
 
     - name: cargo test
       run: cargo test --lib
-      continue-on-error: true
 
     - name: rustfmt
       run: cargo fmt --all -- --check
-      continue-on-error: true
 
     - name: clippy
       run: cargo clippy --lib --tests -- -D warnings
-      continue-on-error: true
+      if: always()
 
     - name: full run
       run: cargo run --release
-      continue-on-error: true
+      if: always()

Cargo.lock

@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "ahash"
@@ -70,6 +70,8 @@ dependencies = [
  "colored",
  "grid",
  "itertools",
+ "misc",
+ "nom",
  "rayon",
  "regex",
  "rustc-hash",
@@ -144,9 +146,9 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "colored"
-version = "2.1.0"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cbf2150cce219b664a8a70df7a1f933836724b503f8a413af9365b4dcc4d90b8"
+checksum = "117725a109d387c937a1533ce01b450cbde6b88abceea8473c4d7a85853cda3c"
 dependencies = [
  "lazy_static",
  "windows-sys",
@@ -154,9 +156,9 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-deque"
-version = "0.8.5"
+version = "0.8.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "613f8cc01fe9cf1a3eb3d7f488fd2fa8388403e97039e2f73692932e291a770d"
+checksum = "9dd111b7b7f7d55b72c0a6ae361660ee5853c9af73f70c3c2ef6858b950e2e51"
 dependencies = [
  "crossbeam-epoch",
  "crossbeam-utils",
@@ -173,9 +175,9 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-utils"
-version = "0.8.20"
+version = "0.8.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22ec99545bb0ed0ea7bb9b8e1e9122ea386ff8a48c0922e43f36d45ab09e0e80"
+checksum = "d0a5c400df2834b80a4c3327b3aad3a4c4cd4de0629063962b03235697506a28"
 
 [[package]]
 name = "darling"
@@ -287,6 +289,29 @@ version = "2.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
+[[package]]
+name = "minimal-lexical"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
+
+[[package]]
+name = "misc"
+version = "0.1.0"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "nom"
+version = "7.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d273983c5a657a70a3e8f2a01329822f3b8c8172b73826411a55751e404a0a4a"
+dependencies = [
+ "memchr",
+ "minimal-lexical",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -549,22 +574,23 @@ dependencies = [
 
 [[package]]
 name = "windows-sys"
-version = "0.48.0"
+version = "0.59.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "677d2418bec65e3338edb076e806bc1ec15693c5d0104683f2efe857f61056a9"
+checksum = "1e38bc4d79ed67fd075bcc251a1c39b32a1776bbe92e5bef1f0bf1f8c531853b"
 dependencies = [
  "windows-targets",
 ]
 
 [[package]]
 name = "windows-targets"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9a2fa6e2155d7247be68c096456083145c183cbbbc2764150dda45a87197940c"
+checksum = "9b724f72796e036ab90c1021d4780d4d3d648aca59e491e6b98e725b84e99973"
 dependencies = [
  "windows_aarch64_gnullvm",
  "windows_aarch64_msvc",
  "windows_i686_gnu",
+ "windows_i686_gnullvm",
  "windows_i686_msvc",
  "windows_x86_64_gnu",
  "windows_x86_64_gnullvm",
@@ -573,45 +599,51 @@ dependencies = [
 
 [[package]]
 name = "windows_aarch64_gnullvm"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2b38e32f0abccf9987a4e3079dfb67dcd799fb61361e53e2882c3cbaf0d905d8"
+checksum = "32a4622180e7a0ec044bb555404c800bc9fd9ec262ec147edd5989ccd0c02cd3"
 
 [[package]]
 name = "windows_aarch64_msvc"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc35310971f3b2dbbf3f0690a219f40e2d9afcf64f9ab7cc1be722937c26b4bc"
+checksum = "09ec2a7bb152e2252b53fa7803150007879548bc709c039df7627cabbd05d469"
 
 [[package]]
 name = "windows_i686_gnu"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a75915e7def60c94dcef72200b9a8e58e5091744960da64ec734a6c6e9b3743e"
+checksum = "8e9b5ad5ab802e97eb8e295ac6720e509ee4c243f69d781394014ebfe8bbfa0b"
+
+[[package]]
+name = "windows_i686_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0eee52d38c090b3caa76c563b86c3a4bd71ef1a819287c19d586d7334ae8ed66"
 
 [[package]]
 name = "windows_i686_msvc"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8f55c233f70c4b27f66c523580f78f1004e8b5a8b659e05a4eb49d4166cca406"
+checksum = "240948bc05c5e7c6dabba28bf89d89ffce3e303022809e73deaefe4f6ec56c66"
 
 [[package]]
 name = "windows_x86_64_gnu"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
+checksum = "147a5c80aabfbf0c7d901cb5895d1de30ef2907eb21fbbab29ca94c5b08b1a78"
 
 [[package]]
 name = "windows_x86_64_gnullvm"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
+checksum = "24d5b23dc417412679681396f2b49f3de8c1473deb516bd34410872eff51ed0d"
 
 [[package]]
 name = "windows_x86_64_msvc"
-version = "0.48.5"
+version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
+checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
 
 [[package]]
 name = "zerocopy"

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
+edition = "2021"
 name = "aoc2024"
 version = "0.1.0"
-edition = "2021"
 
 [dependencies]
 aoc-runner = "0.3.0"
@@ -10,8 +10,10 @@ atoi = "2.0.0"
 bitflags = "2.6.0"
 cached = "0.54.0"
 colored = "2.1.0"
-grid = { version = "0.1.0", path = "utils/grid" }
+grid = {version = "0.1.0", path = "utils/grid"}
 itertools = "0.13.0"
+misc = {path = "utils/misc"}
+nom = "7.1.3"
 rayon = "1.10.0"
 regex = "1.11.1"
 rustc-hash = "2.1.0"
@@ -19,3 +21,5 @@ thread_local = "1.1.8"
 
 [profile.release]
 lto = true
+opt-level = 3
+overflow-checks = false

README.md

@@ -1,6 +1,6 @@
 <!-- AOC TILES BEGIN -->
 <h1 align="center">
-  2024 - 32 ⭐ - Rust
+  2024 - 48 ⭐ - Rust
 </h1>
 <a href="src/day1.rs">
   <img src=".aoc_tiles/tiles/2024/01.png" width="161px">
@@ -50,4 +50,31 @@
 <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/day10.rs

@@ -25,7 +25,7 @@ impl TrailMap {
             .iter()
             .enumerate()
             .filter(|(_, v)| **v == b'0')
-            .map(|(i, _v)| self.map.coord(i as i64).unwrap())
+            .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 {

src/day14.rs

@@ -1,12 +1,26 @@
 use aoc_runner_derive::aoc;
 use colored::Colorize;
-use grid::{AsCoord2d, Coord2d, Grid};
-use regex::Regex;
-use std::str::FromStr;
+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: Coord2d,
-    vel: Coord2d,
+    pos: Coord,
+    vel: (i64, i64),
+}
+
+struct Robots {
+    robots: Vec<Robot>,
+    width: i64,
+    height: i64,
 }
 
 #[derive(Debug, Eq, PartialEq)]
@@ -17,52 +31,37 @@ enum Quadrant {
     SE = 3,
 }
 
-impl FromStr for Robot {
-    type Err = Box<dyn std::error::Error>;
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let re = Regex::new(r"p=(\d+),(\d+) v=([+-]?\d+),([+-]?\d+)").unwrap();
-        match re.captures(s) {
-            Some(c) => Ok(Self {
-                pos: (
-                    c.get(1).unwrap().as_str().parse::<i64>().unwrap(),
-                    c.get(2).unwrap().as_str().parse().unwrap(),
-                )
-                    .to_coord(),
-                vel: (
-                    c.get(3).unwrap().as_str().parse::<i64>().unwrap(),
-                    c.get(4).unwrap().as_str().parse().unwrap(),
-                )
-                    .to_coord(),
-            }),
-            None => panic!(),
-        }
-    }
+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 step(&mut self, bounds: (i64, i64)) {
-        let mut candidate_new_pos = ((self.pos.x() + self.vel.x()), (self.pos.y() + self.vel.y()));
-        if candidate_new_pos.0 < 0 {
-            // if pos goes negative, add the upper bound
-            candidate_new_pos.0 += bounds.0;
+    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,
         }
-        if candidate_new_pos.1 < 0 {
-            candidate_new_pos.1 += bounds.1;
-        }
-        candidate_new_pos.0 %= bounds.0;
-        candidate_new_pos.1 %= bounds.1;
-
-        self.pos = candidate_new_pos.to_coord();
+    }
+    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.x() < splits.0 && self.pos.y() < splits.1 {
+        if self.pos.0 < splits.0 && self.pos.1 < splits.1 {
             Some(Quadrant::NW)
-        } else if self.pos.x() > splits.0 && self.pos.y() < splits.1 {
+        } else if self.pos.0 > splits.0 && self.pos.1 < splits.1 {
             Some(Quadrant::NE)
-        } else if self.pos.x() < splits.0 && self.pos.y() > splits.1 {
+        } else if self.pos.0 < splits.0 && self.pos.1 > splits.1 {
             Some(Quadrant::SW)
-        } else if self.pos.x() > splits.0 && self.pos.y() > splits.1 {
+        } else if self.pos.0 > splits.0 && self.pos.1 > splits.1 {
             Some(Quadrant::SE)
         } else {
             None
@@ -70,49 +69,58 @@ impl Robot {
     }
 }
 
-#[allow(dead_code)]
-fn display(robots: &Vec<Robot>, bounds: (i64, i64)) {
-    let grid = as_grid(robots, bounds);
-    for row in 0..grid.height() {
-        for col in 0..grid.width() {
-            print!(
-                "{}",
-                if *grid.get(&(col, row)).unwrap() != 0 {
-                    "█".green()
-                } else {
-                    " ".color(colored::Color::Black)
-                }
-            );
+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)
         }
-        println!();
     }
 }
 
-fn as_grid(robots: &Vec<Robot>, bounds: (i64, i64)) -> Grid<usize> {
-    let mut grid = Grid::with_shape(bounds.0 as usize, bounds.1 as usize, 0);
-    for r in robots {
-        grid.increment(&r.pos, 1usize);
+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(())
     }
-    grid
 }
 
-fn parse(input: &str) -> Vec<Robot> {
-    input.lines().map(|l| l.parse().unwrap()).collect()
+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 = parse(input);
-    for _ in 0..100 {
-        for r in &mut robots {
-            r.step((width, height))
-        }
-    }
-    let mut counts = [0; 4];
-    for r in robots {
-        if let Some(q) = r.quad((width, height)) {
-            counts[q as usize] += 1
-        }
-    }
+    let mut robots = Robots::from_vec(parse(input, width, height), width, height);
+    robots.step(100);
+    let counts = robots.count_quads();
     counts.iter().product()
 }
 
@@ -125,19 +133,16 @@ pub fn part1(input: &str) -> u64 {
 pub fn part2(input: &str) -> u64 {
     let width = 101;
     let height = 103;
-    let mut robots = parse(input);
+    let mut robots = Robots::from_vec(parse(input, width, height), width, height);
     for i in 1.. {
-        for r in &mut robots {
-            r.step((width, height))
-        }
+        robots.step(1);
         // collect into lines
-        let g = as_grid(&robots, (width, height));
+        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)
         {
-            display(&robots, (width, height));
             return i;
         }
     }

src/day15.rs

@@ -16,7 +16,7 @@ impl Display for Warehouse {
 
 impl Warehouse {
     fn step_robot(&mut self, dir: Move) {
-        let start = self.robot_pos.clone();
+        let start = self.robot_pos;
         if self.push(&start, &dir) {
             self.robot_pos = &self.robot_pos + dir.ofs();
         }
@@ -40,12 +40,12 @@ impl Warehouse {
                     // move both parts
                     self.push(&target, dir);
                     self.push(&(&target + (-1, 0)), dir);
-                    self.map.swap(&target, pos);
+                    self.map.swap(target, pos);
                 }
                 b'[' => {
                     self.push(&target, dir);
                     self.push(&(&target + (1, 0)), dir);
-                    self.map.swap(&target, pos);
+                    self.map.swap(target, pos);
                 }
                 c => panic!("unexpected char {}", c),
             }

src/day16.rs

@@ -1,13 +1,14 @@
 use aoc_runner_derive::aoc;
-use grid::{AsCoord2d, Coord2d, Grid};
-use itertools::Itertools;
+use grid::{Coord2d, Grid};
 use std::{
+    cmp::Ordering,
     collections::{BinaryHeap, HashMap},
-    i64,
     str::FromStr,
-    usize,
 };
 
+type CoordType = i16;
+type Coord = (CoordType, CoordType);
+
 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Ord, PartialOrd)]
 enum FacingDirection {
     East,
@@ -17,7 +18,7 @@ enum FacingDirection {
 }
 
 impl FacingDirection {
-    fn ofs(&self) -> (i64, i64) {
+    fn ofs(&self) -> (CoordType, CoordType) {
         match self {
             FacingDirection::East => (1, 0),
             FacingDirection::South => (0, 1),
@@ -25,11 +26,13 @@ impl FacingDirection {
             FacingDirection::North => (0, -1),
         }
     }
-    fn reachable(&self) -> [FacingDirection; 3] {
+    fn reachable(&self) -> &[FacingDirection; 3] {
         // Can move perpendicularly or the same direction, backwards would always increase path cost
         match self {
-            FacingDirection::East | FacingDirection::West => [*self, FacingDirection::North, FacingDirection::South],
-            FacingDirection::South | FacingDirection::North => [*self, FacingDirection::East, FacingDirection::West],
+            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],
         }
     }
 }
@@ -37,9 +40,8 @@ impl FacingDirection {
 #[derive(Clone, Eq, PartialEq, Debug)]
 struct State {
     cost: usize,
-    position: Coord2d,
+    position: Coord,
     facing: FacingDirection,
-    path: Vec<Coord2d>,
 }
 
 impl Ord for State {
@@ -58,94 +60,156 @@ impl PartialOrd for State {
     }
 }
 
+#[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>,
-    paths: HashMap<usize, Vec<Vec<Coord2d>>>,
 }
 
 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()?;
-        let paths = HashMap::new();
 
-        Ok(Self { map, paths })
+        Ok(Self { map })
     }
 }
 
 impl Maze {
-    fn dijkstra<const RECORD_PATHS: bool>(&mut self) -> usize {
-        let start = self.map.find(&b'S').expect("can't find start").to_coord();
-        let finish = self.map.find(&b'E').expect("can't find finish").to_coord();
+    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::with_capacity(self.map.data.len());
-        let mut best_cost = usize::MAX;
+        let mut queue = BinaryHeap::new();
 
         distances.insert((start, FacingDirection::East), 0);
         queue.push(State {
             cost: 0,
             position: start,
             facing: FacingDirection::East,
-            path: Vec::new(),
         });
 
-        while let Some(State {
-            cost,
-            position,
-            facing,
-            path,
-        }) = queue.pop()
-        {
-            let mut new_path = path.clone();
-            new_path.push(position);
-
-            if position == finish {
-                if RECORD_PATHS {
-                    if cost < best_cost {
-                        best_cost = cost
-                    }
-                    if !self.paths.contains_key(&cost) {
-                        self.paths.insert(cost, vec![new_path.clone()]);
-                    } else {
-                        self.paths.get_mut(&cost).unwrap().push(new_path.clone());
-                    }
-                    continue;
-                } else {
-                    return cost;
-                }
+        while let Some(state) = queue.pop() {
+            if state.position == finish {
+                return state.cost;
             }
 
-            if distances.get(&(position, facing)).is_some_and(|v| cost > *v) {
+            if distances
+                .get(&(state.position, state.facing))
+                .is_some_and(|v| state.cost > *v)
+            {
                 continue;
             }
 
-            for (new_dir, new_position, new_cost) in facing
-                .reachable()
-                .iter()
-                .map(|dir| (dir, &position + dir.ofs()))
-                .filter(|(_, pos)| self.map.get(pos).is_some_and(|c| *c != b'#'))
-                .map(|(dir, pos)| (dir, pos, if *dir == facing { cost + 1 } else { cost + 1001 }))
-            {
+            for new_state in self.valid_moves(&state) {
                 if distances
-                    .get(&(new_position, *new_dir))
-                    .is_none_or(|best_cost| new_cost <= *best_cost)
+                    .get(&(new_state.position, new_state.facing))
+                    .is_none_or(|best_cost| new_state.cost < *best_cost)
                 {
-                    queue.push(State {
-                        cost: new_cost,
-                        position: new_position,
-                        facing: *new_dir,
-                        path: new_path.clone(),
-                    });
-                    distances.insert((new_position, *new_dir), new_cost);
+                    distances.insert((new_state.position, new_state.facing), new_state.cost);
+                    queue.push(new_state);
                 }
             }
         }
-        if best_cost == usize::MAX || !RECORD_PATHS {
-            panic!("no path found");
-        } else {
-            return best_cost;
+        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)
     }
 }
 
@@ -155,22 +219,20 @@ fn parse(input: &str) -> Maze {
 
 #[aoc(day16, part1)]
 pub fn part1(input: &str) -> usize {
-    let mut maze = parse(input);
-    maze.dijkstra::<false>()
+    let maze = parse(input);
+    maze.dijkstra()
 }
 
 #[aoc(day16, part2)]
 pub fn part2(input: &str) -> usize {
     let mut maze = parse(input);
-    let best_cost = maze.dijkstra::<true>();
-    let best_paths = maze.paths.get(&best_cost).unwrap();
-    let best_path_tiles = best_paths.into_iter().flatten().collect_vec();
+    let best_paths = maze.path_dijkstra();
 
-    let mut path_map = maze.map.clone();
-    for tile in best_path_tiles {
-        path_map.set(&tile, b'O');
+    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(&b'O')
+    path_map.count(&true)
 }
 
 #[cfg(test)]

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/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/day6.rs

@@ -99,13 +99,12 @@ pub struct Map {
 impl<T: BufRead> From<T> for Map {
     fn from(input: T) -> Self {
         let grid = Grid::from(input);
-        let mut visited_from: Grid<DirectionSet> = Grid::new(grid.width() as i64);
-        visited_from.data.resize(grid.data.len(), DirectionSet::empty());
+        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: guard_pos.into(),
             guard_facing,
             visited_from,
             path: Vec::new(),

src/day8.rs

@@ -42,9 +42,9 @@ impl AntennaMap {
                 // 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.0 - b.0, a.1 - b.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.0 + i * offset.0, a.1 + i * offset.1);
+                    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;

src/lib.rs

@@ -1,6 +1,3 @@
-mod day16;
-use aoc_runner_derive::aoc_lib;
-
 pub mod day1;
 pub mod day10;
 pub mod day11;
@@ -8,7 +5,17 @@ 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;
@@ -17,4 +24,5 @@ pub mod day7;
 pub mod day8;
 pub mod day9;
 
+use aoc_runner_derive::aoc_lib;
 aoc_lib! { year = 2024 }

utils/grid/lib.rs

@@ -1,7 +1,7 @@
 use std::{
     fmt::{Debug, Display, Formatter, Write},
     io::{BufRead, Cursor},
-    iter::repeat,
+    iter::repeat_n,
     mem::swap,
     ops::{Add, AddAssign, Sub},
     str::FromStr,
@@ -39,6 +39,16 @@ impl<T: AsCoord2d> Add<T> for &Coord2d {
     }
 }
 
+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
@@ -63,86 +73,120 @@ impl AsCoord2d for &Coord2d {
     }
 }
 
-impl AsCoord2d for (i32, i32) {
+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.into(),
-            y: self.1.into(),
+            x: self.0.try_into().unwrap(),
+            y: self.1.try_into().unwrap(),
         }
     }
     fn x(&self) -> i64 {
-        self.0.into()
+        self.0.try_into().unwrap()
     }
     fn y(&self) -> i64 {
-        self.1.into()
+        self.1.try_into().unwrap()
     }
 }
 
-impl AsCoord2d for (i64, i64) {
-    fn to_coord(self) -> Coord2d {
-        Coord2d { x: self.0, y: self.1 }
-    }
-    fn x(&self) -> i64 {
-        self.0
-    }
-    fn y(&self) -> i64 {
-        self.1
-    }
-}
-
-impl AsCoord2d for (usize, usize) {
+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 as i64,
-            y: self.1 as i64,
+            x: self.0.try_into().unwrap(),
+            y: self.1.try_into().unwrap(),
         }
     }
     fn x(&self) -> i64 {
-        self.0 as i64
+        self.0.try_into().unwrap()
     }
     fn y(&self) -> i64 {
-        self.1 as i64
+        self.1.try_into().unwrap()
     }
 }
 
-impl AsCoord2d for (u64, u64) {
-    fn to_coord(self) -> Coord2d {
-        Coord2d {
-            x: self.0 as i64,
-            y: self.1 as i64,
+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,
         }
     }
-    fn x(&self) -> i64 {
-        self.0 as i64
+}
+
+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 y(&self) -> i64 {
-        self.1 as i64
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.grid.height() - 1, Some(self.grid.height() - 1))
     }
 }
 
-#[derive(Clone, Eq, PartialEq)]
+#[derive(Clone, Eq, PartialEq, Debug)]
 pub struct Grid<T> {
     pub data: Vec<T>,
     width: i64,
 }
 
 impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
-    pub fn new(width: i64) -> Self {
-        Self {
-            data: Vec::new(),
-            width,
-        }
-    }
     /// 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 {
-            data: Vec::from_iter(repeat(fill).take(self.width() * self.height())),
-            width: self.width,
-        }
+        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(fill).take(width * height)),
+            data: Vec::from_iter(repeat_n(fill, width * height)),
             width: width as i64,
         }
     }
@@ -155,18 +199,33 @@ impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
     pub fn pos<C: AsCoord2d>(&self, c: &C) -> i64 {
         c.y() * self.width + c.x()
     }
-    pub fn coord(&self, pos: i64) -> Option<(i64, i64)> {
+    pub fn coord(&self, pos: i64) -> Option<Coord2d> {
         if pos < 0 || pos >= self.data.len() as i64 {
             None
         } else {
-            Some((pos % self.width, pos / self.width))
+            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() >= self.data.len() as i64 / self.width {
+        if c.y() < 0 || c.y() as usize >= self.height() {
             return None;
         }
         let pos = self.pos(c);
@@ -216,15 +275,31 @@ impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
         }
     }
 
-    pub fn col(&self, x: i64) -> Option<Vec<&T>> {
-        if x < self.width() as i64 && x >= 0 {
-            Some((0..self.height()).map(|y| self.get(&(x, y as i64)).unwrap()).collect())
+    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 find(&self, haystack: &T) -> Option<(i64, i64)> {
+    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()
@@ -246,9 +321,8 @@ impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
     }
 
     pub fn swap<A: AsCoord2d, B: AsCoord2d>(&mut self, a: A, b: B) {
-        match (self.valid_pos(&a), self.valid_pos(&b)) {
-            (Some(a), Some(b)) => self.data.swap(a, b),
-            _ => {}
+        if let (Some(a), Some(b)) = (self.valid_pos(&a), self.valid_pos(&b)) {
+            self.data.swap(a, b)
         }
     }
 
@@ -323,6 +397,24 @@ impl Display for Grid<u8> {
     }
 }
 
+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::*;
@@ -371,6 +463,28 @@ FBCG";
         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();

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

@@ -0,0 +1,7 @@
+[package]
+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);
+    }
+}