Day 15: Warehouse Woes

README.md

@@ -19,6 +19,6 @@ Development occurs in language-specific directories:
 |[Day12.hs](hs/src/Day12.hs)|[Day12.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day12.kt)|[day12.py](py/aoc2024/day12.py)|[day12.rs](rs/src/day12.rs)|
 |[Day13.hs](hs/src/Day13.hs)|[Day13.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day13.kt)|[day13.py](py/aoc2024/day13.py)|[day13.rs](rs/src/day13.rs)|
 |[Day14.hs](hs/src/Day14.hs)|[Day14.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day14.kt)|[day14.py](py/aoc2024/day14.py)|[day14.rs](rs/src/day14.rs)|
-|[Day15.hs](hs/src/Day15.hs)|[Day15.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day15.kt)|[day15.py](py/aoc2024/day15.py)||
+|[Day15.hs](hs/src/Day15.hs)|[Day15.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day15.kt)|[day15.py](py/aoc2024/day15.py)|[day15.rs](rs/src/day15.rs)|
 |[Day16.hs](hs/src/Day16.hs)|[Day16.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day16.kt)|[day16.py](py/aoc2024/day16.py)||
 |[Day17.hs](hs/src/Day17.hs)|[Day17.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day17.kt)|||

rs/benches/criterion.rs

@@ -1,5 +1,5 @@
 use aoc2024::{
-    day1, day10, day11, day12, day13, day14, day2, day3, day4, day5, day6, day7, day8, day9,
+    day1, day10, day11, day12, day13, day14, day15, day2, day3, day4, day5, day6, day7, day8, day9,
 };
 use criterion::{black_box, Criterion};
 use std::env;
@@ -100,6 +100,12 @@ fn aoc2024_bench(c: &mut Criterion) -> io::Result<()> {
     g.bench_function("part 2", |b| b.iter(|| day14::part2(black_box(&data))));
     g.finish();
 
+    let data = get_day_input(15)?;
+    let mut g = c.benchmark_group("day 15");
+    g.bench_function("part 1", |b| b.iter(|| day15::part1(black_box(&data))));
+    g.bench_function("part 2", |b| b.iter(|| day15::part2(black_box(&data))));
+    g.finish();
+
     Ok(())
 }
 

rs/src/day15.rs

@@ -0,0 +1,189 @@
+use std::collections::BTreeSet;
+use std::ops::IndexMut;
+
+type YX = (usize, usize);
+
+fn parse(data: &str) -> Option<(Vec<Vec<u8>>, YX, &str)> {
+    let (map, moves) = data.split_once("\n\n").unwrap_or((data, ""));
+    let map = map
+        .lines()
+        .map(|line| line.bytes().collect())
+        .collect::<Vec<Vec<_>>>();
+    let robot = map.iter().enumerate().find_map(|(y, line)| {
+        line.iter()
+            .enumerate()
+            .find(|(_, b)| **b == b'@')
+            .map(|(x, _)| (y, x))
+    });
+    Some((map, robot?, moves))
+}
+
+fn move_robot<Line>(map: &mut [Line], robot: YX, c: char) -> Option<YX>
+where
+    Line: IndexMut<usize, Output = u8>,
+{
+    let (dy, dx) = match c {
+        '^' => (usize::MAX, 0),
+        'v' => (1, 0),
+        '<' => (0, usize::MAX),
+        '>' => (0, 1),
+        _ => return None,
+    };
+    let mut levels = vec![];
+    let mut front: BTreeSet<_> = [robot].into();
+    while !front.is_empty() {
+        let back = front;
+        front = BTreeSet::new();
+        for (y, x) in &back {
+            let (y, x) = (y.wrapping_add(dy), x.wrapping_add(dx));
+            match map[y][x] {
+                b'.' => continue,
+                b'O' => {
+                    front.insert((y, x));
+                }
+                b'[' => {
+                    front.insert((y, x));
+                    if dy != 0 {
+                        front.insert((y, x + 1));
+                    }
+                }
+                b']' => {
+                    front.insert((y, x));
+                    if dy != 0 {
+                        front.insert((y, x - 1));
+                    }
+                }
+                _ => return None,
+            }
+        }
+        levels.push(back);
+    }
+    for front in levels.into_iter().rev() {
+        for (y, x) in front {
+            map[y.wrapping_add(dy)][x.wrapping_add(dx)] = map[y][x];
+            map[y][x] = b'.';
+        }
+    }
+    Some((robot.0.wrapping_add(dy), robot.1.wrapping_add(dx)))
+}
+
+pub fn part1(data: &str) -> Option<usize> {
+    let (mut map, mut robot, moves) = parse(data)?;
+    for c in moves.chars() {
+        robot = move_robot(&mut map, robot, c).unwrap_or(robot);
+    }
+    Some(
+        map.into_iter()
+            .enumerate()
+            .flat_map(|(y, line)| {
+                line.into_iter().enumerate().filter_map(move |(x, b)| {
+                    if b == b'O' {
+                        Some(100 * y + x)
+                    } else {
+                        None
+                    }
+                })
+            })
+            .sum(),
+    )
+}
+
+pub fn part2(data: &str) -> Option<usize> {
+    let (mut map, mut robot, moves) = parse(data)?;
+    for line in &mut map {
+        *line = line
+            .iter()
+            .flat_map(|&b| match b {
+                b'@' => *b"@.",
+                b'O' => *b"[]",
+                _ => [b, b],
+            })
+            .collect();
+    }
+    robot.1 *= 2;
+    for c in moves.chars() {
+        robot = move_robot(&mut map, robot, c).unwrap_or(robot);
+    }
+    Some(
+        map.into_iter()
+            .enumerate()
+            .flat_map(|(y, line)| {
+                line.into_iter().enumerate().filter_map(move |(x, b)| {
+                    if b == b'[' {
+                        Some(100 * y + x)
+                    } else {
+                        None
+                    }
+                })
+            })
+            .sum(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE_1: &str = indoc! {"
+        ##########
+        #..O..O.O#
+        #......O.#
+        #.OO..O.O#
+        #[email protected].#
+        #O#..O...#
+        #O..O..O.#
+        #.OO.O.OO#
+        #....O...#
+        ##########
+
+        <vv>^<v^>v>^vv^v>v<>v^v<v<^vv<<<^><<><>>v<vvv<>^v^>^<<<><<v<<<v^vv^v>^
+        vvv<<^>^v^^><<>>><>^<<><^vv^^<>vvv<>><^^v>^>vv<>v<<<<v<^v>^<^^>>>^<v<v
+        ><>vv>v^v^<>><>>>><^^>vv>v<^^^>>v^v^<^^>v^^>v^<^v>v<>>v^v^<v>v^^<^^vv<
+        <<v<^>>^^^^>>>v^<>vvv^><v<<<>^^^vv^<vvv>^>v<^^^^v<>^>vvvv><>>v^<<^^^^^
+        ^><^><>>><>^^<<^^v>>><^<v>^<vv>>v>>>^v><>^v><<<<v>>v<v<v>vvv>^<><<>^><
+        ^>><>^v<><^vvv<^^<><v<<<<<><^v<<<><<<^^<v<^^^><^>>^<v^><<<^>>^v<v^v<v^
+        >^>>^v>vv>^<<^v<>><<><<v<<v><>v<^vv<<<>^^v^>^^>>><<^v>>v^v><^^>>^<>vv^
+        <><^^>^^^<><vvvvv^v<v<<>^v<v>v<<^><<><<><<<^^<<<^<<>><<><^^^>^^<>^>v<>
+        ^^>vv<^v^v<vv>^<><v<^v>^^^>>>^^vvv^>vvv<>>>^<^>>>>>^<<^v>^vvv<>^<><<v>
+        v^^>>><<^^<>>^v^<v^vv<>v^<<>^<^v^v><^<<<><<^<v><v<>vv>>v><v^<vv<>v^<<^
+    "};
+
+    static EXAMPLE_2: &str = indoc! {"
+        ########
+        #..O.O.#
+        ##@.O..#
+        #...O..#
+        #.#.O..#
+        #...O..#
+        #......#
+        ########
+
+        <^^>>>vv<v>>v<<
+    "};
+
+    static EXAMPLE_3: &str = indoc! {"
+        #######
+        #...#.#
+        #.....#
+        #..OO@#
+        #..O..#
+        #.....#
+        #######
+
+        <vv<<^^<<^^
+    "};
+
+    #[test]
+    fn part1_examples() {
+        assert_eq!(Some(2028), part1(EXAMPLE_2));
+        assert_eq!(Some(10092), part1(EXAMPLE_1));
+    }
+
+    #[test]
+    fn part2_examples() {
+        assert_eq!(Some(618), part2(EXAMPLE_3));
+        assert_eq!(Some(9021), part2(EXAMPLE_1));
+    }
+}

rs/src/lib.rs

@@ -4,6 +4,7 @@ pub mod day11;
 pub mod day12;
 pub mod day13;
 pub mod day14;
+pub mod day15;
 pub mod day2;
 pub mod day3;
 pub mod day4;

rs/src/main.rs

@@ -1,6 +1,6 @@
 use anyhow::anyhow;
 use aoc2024::{
-    day1, day10, day11, day12, day13, day14, day2, day3, day4, day5, day6, day7, day8, day9,
+    day1, day10, day11, day12, day13, day14, day15, day2, day3, day4, day5, day6, day7, day8, day9,
 };
 use std::collections::HashSet;
 use std::env;
@@ -131,5 +131,13 @@ fn main() -> anyhow::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains("15") {
+        println!("Day 15");
+        let data = get_day_input(15)?;
+        println!("{:?}", day15::part1(&data).ok_or(anyhow!("None"))?);
+        println!("{:?}", day15::part2(&data).ok_or(anyhow!("None"))?);
+        println!();
+    }
+
     Ok(())
 }