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()

README.md

@@ -1,6 +1,6 @@
 <!-- AOC TILES BEGIN -->
 <h1 align="center">
-  2024 - 36 ⭐ - Rust
+  2024 - 48 ⭐ - Rust
 </h1>
 <a href="src/day1.rs">
   <img src=".aoc_tiles/tiles/2024/01.png" width="161px">
@@ -56,4 +56,25 @@
 <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/day16.rs

@@ -1,5 +1,5 @@
 use aoc_runner_derive::aoc;
-use grid::Grid;
+use grid::{Coord2d, Grid};
 use std::{
     cmp::Ordering,
     collections::{BinaryHeap, HashMap},
@@ -108,10 +108,10 @@ impl Maze {
             })
     }
     fn dijkstra(&self) -> usize {
-        let (start_x, start_y) = self.map.find(&b'S').expect("can't find start");
+        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 (finish_x, finish_y) = self.map.find(&b'E').expect("can't find finish");
+        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();
@@ -149,10 +149,11 @@ impl Maze {
         usize::MAX
     }
     fn path_dijkstra(&mut self) -> (usize, Vec<Vec<Coord>>) {
-        let (start_x, start_y) = self.map.find(&b'S').expect("can't find start");
+        let Coord2d {x: start_x, y: start_y} = self.map.find(&b'S').expect("can't find start");
-        let start = (start_x.try_into().unwrap(), start_y.try_into().unwrap());
+        let start = (start_x as CoordType, start_y as CoordType);
-        let (finish_x, finish_y) = self.map.find(&b'E').expect("can't find finish");
+
-        let finish = (finish_x.try_into().unwrap(), finish_y.try_into().unwrap());
+        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());

src/day18.rs

@@ -1,7 +1,10 @@
 use aoc_runner_derive::aoc;
 use grid::Grid;
 use itertools::Itertools;
-use std::{cmp::Reverse, collections::BinaryHeap};
+use std::{
+    cmp::Reverse,
+    collections::{BinaryHeap, VecDeque},
+};
 
 #[derive(Clone)]
 struct MemoryMap {
@@ -10,6 +13,7 @@ struct MemoryMap {
 }
 
 trait PathTrack {
+    const DOES_WORK: bool = true;
     fn new() -> Self;
     fn push(&mut self, pos: (i64, i64));
     fn finalize(&mut self) {}
@@ -37,6 +41,15 @@ impl PathTrack for Vec<(i64, i64)> {
     }
 }
 
+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);
@@ -51,17 +64,14 @@ impl MemoryMap {
 
         Self { map, byte_stream }
     }
-    // Return if the byte caused a new blockage or not
+
-    fn place_byte(&mut self, i: usize) -> bool {
+    fn place_byte(&mut self, i: usize) {
         let pos = self.byte_stream[i];
-        match self.map.set(&pos, false) {
+        self.map.set(&pos, false);
-            None => panic!("corruption outside memory bounds"),
-            Some(x) => x,
-        }
     }
-    fn place_bytes(&mut self, n: usize) {
+
-        assert!(n < self.byte_stream.len());
+    fn place_bytes(&mut self, start: usize, end: usize) {
-        for i in 0..n {
+        for i in start..=end {
             self.place_byte(i);
         }
     }
@@ -73,6 +83,54 @@ impl MemoryMap {
             .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);
 
@@ -85,16 +143,20 @@ impl MemoryMap {
 
         while let Some((cost, pos)) = queue.pop() {
             if pos == goal {
-                let mut visited_pos = goal;
+                if T::DOES_WORK {
-                let mut path = T::new();
+                    let mut visited_pos = goal;
-                path.push(pos);
+                    let mut path = T::new();
-                while let Some(next) = prev.get(&visited_pos) {
+                    path.push(pos);
-                    visited_pos = *next;
+                    while let Some(next) = prev.get(&visited_pos) {
-                    path.push(*next);
+                        visited_pos = *next;
-                    if *next == start {
+                        path.push(*next);
-                        path.finalize();
+                        if *next == start {
-                        return Some(path);
+                            path.finalize();
+                            return Some(path);
+                        }
                     }
+                } else {
+                    return Some(T::new());
                 }
             }
 
@@ -106,7 +168,9 @@ impl MemoryMap {
             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);
-                    prev.set(&new_pos, pos);
+                    if T::DOES_WORK {
+                        prev.set(&new_pos, pos);
+                    }
                     queue.push((Reverse(cost.0 + 1), new_pos));
                 }
             }
@@ -115,37 +179,56 @@ impl MemoryMap {
     }
 }
 
-pub fn part1_impl(input: &str, width: usize, height: usize, n: usize) -> usize {
+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(n);
+    map.place_bytes(0, initial_safe_byte_count - 1);
-    let path = map.dijkstra::<LengthPath>((0, 0)).expect("no path found");
+    let path = map.bfs::<LengthPath>((0, 0)).expect("no path found");
 
     path.0 - 1 // count edges, not visited nodes (start doesn't count)
 }
 
-pub fn part2_impl(input: &str, width: usize, height: usize, n: usize) -> (i64, i64) {
+// 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);
 
-    input_map.place_bytes(n);
+    let mut path = input_map.bfs::<Vec<(i64, i64)>>((0, 0)).expect("no path found");
-    let mut path = input_map.dijkstra::<Vec<(i64, i64)>>((0, 0)).expect("no path found");
 
-    for byte in n..input_map.byte_stream.len() {
+    for byte in initial_safe_byte_count..input_map.byte_stream.len() {
-        if input_map.place_byte(byte) {
+        input_map.place_byte(byte);
-            // If it's a new blockage, and it obstructs our best path, we need to do a new path search
+        // 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]) {
+        if let Some((obs_at, _)) = path.iter().find_position(|v| *v == &input_map.byte_stream[byte]) {
-                let (before, _) = path.split_at(obs_at);
+            let (before, _) = path.split_at(obs_at);
 
-                if let Some(new_path) = input_map.dijkstra::<Vec<(i64, i64)>>(path[obs_at - 1]) {
+            if let Some(new_path) = input_map.bfs::<Vec<(i64, i64)>>(path[obs_at - 1]) {
-                    path = [before, &new_path].concat();
+                path = [before, &new_path].concat();
-                } else {
+            } else {
-                    return input_map.byte_stream[byte];
+                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)
@@ -195,4 +278,9 @@ mod tests {
     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);
+        let visited_from = grid.same_shape(DirectionSet::empty());
-        visited_from.data.resize(grid.data.len(), 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

@@ -8,7 +8,14 @@ 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;

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
@@ -82,29 +92,101 @@ where
     }
 }
 
-#[derive(Clone, Eq, PartialEq)]
+impl<T> AsCoord2d for &(T, T)
+where
+    T: Copy + TryInto<i64>,
+    <T as TryInto<i64>>::Error: Debug,
+{
+    fn to_coord(self) -> Coord2d {
+        Coord2d {
+            x: self.0.try_into().unwrap(),
+            y: self.1.try_into().unwrap(),
+        }
+    }
+    fn x(&self) -> i64 {
+        self.0.try_into().unwrap()
+    }
+    fn y(&self) -> i64 {
+        self.1.try_into().unwrap()
+    }
+}
+
+impl From<Coord2d> for (i64, i64) {
+    fn from(value: Coord2d) -> Self {
+        (value.x, value.y)
+    }
+}
+
+#[derive(Debug)]
+pub struct GridRowIter<'a, T> {
+    iter: std::slice::Iter<'a, T>,
+}
+
+impl<'a, T: Clone + Eq + PartialEq + Debug> GridRowIter<'a, T> {
+    fn new(grid: &'a Grid<T>, y: i64) -> Self {
+        let iter = grid.data[y as usize * grid.width()..(y as usize + 1) * grid.width()].iter();
+        Self { iter }
+    }
+}
+
+impl<'a, T> Iterator for GridRowIter<'a, T> {
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        self.iter.next()
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iter.size_hint()
+    }
+}
+
+#[derive(Debug)]
+pub struct GridColIter<'a, T> {
+    grid: &'a Grid<T>,
+    stride: usize,
+    cur: usize,
+}
+
+impl<'a, T: Clone + Eq + PartialEq + Debug> GridColIter<'a, T> {
+    fn new(grid: &'a Grid<T>, x: i64) -> Self {
+        Self {
+            grid,
+            stride: grid.width(),
+            cur: x as usize,
+        }
+    }
+}
+
+impl<'a, T: Clone + Eq + PartialEq + Debug> Iterator for GridColIter<'a, T> {
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        let cur = self.cur;
+        self.cur += self.stride;
+        if cur < self.grid.data.len() {
+            Some(&self.grid.data[cur])
+        } else {
+            None
+        }
+    }
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.grid.height() - 1, Some(self.grid.height() - 1))
+    }
+}
+
+#[derive(Clone, Eq, PartialEq, Debug)]
 pub struct Grid<T> {
     pub data: Vec<T>,
     width: i64,
 }
 
 impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
-    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 {
+        Grid::with_shape(self.width(), self.height(), fill)
-            data: Vec::from_iter(repeat(fill).take(self.width() * self.height())),
-            width: self.width,
-        }
     }
+    /// 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,
         }
     }
@@ -117,13 +199,28 @@ 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;
@@ -178,15 +275,31 @@ impl<T: Clone + Eq + PartialEq + Debug> Grid<T> {
         }
     }
 
-    pub fn col(&self, x: i64) -> Option<Vec<&T>> {
+    pub fn row_iter(&self, y: i64) -> Option<GridRowIter<T>> {
-        if x < self.width() as i64 && x >= 0 {
+        if (y as usize) < self.height() {
-            Some((0..self.height()).map(|y| self.get(&(x, y as i64)).unwrap()).collect())
+            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()
@@ -350,6 +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();