day10: Initial solution

README.md

@@ -18,6 +18,8 @@
   - [solution](src/day08.rs)
 - [Day 9: Mirage Maintenance](https://adventofcode.com/2023/day/9)
   - [solution](src/day09.rs)
+- [Day 10: Pipe Maze](https://adventofcode.com/2023/day/10)
+  - [solution](src/day10.rs)
 <!-- Insert before -->
 
 See:

src/day10.rs

@@ -0,0 +1,175 @@
+use ahash::{HashSet, HashSetExt};
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Debug)]
+enum Dir {
+    Down,
+    Left,
+    Up,
+    Right,
+}
+
+impl Dir {
+    fn next_pos(&self, r: &mut usize, c: &mut usize) {
+        match self {
+            Dir::Down => *r += 1,
+            Dir::Left => *c -= 1,
+            Dir::Up => *r -= 1,
+            Dir::Right => *c += 1,
+        }
+    }
+}
+
+fn next_direction(pipe: u8, dir: &Dir) -> Option<Dir> {
+    Some(match (pipe, dir) {
+        (b'|', Dir::Down) => Dir::Down,
+        (b'|', Dir::Up) => Dir::Up,
+        (b'-', Dir::Left) => Dir::Left,
+        (b'-', Dir::Right) => Dir::Right,
+        (b'L', Dir::Down) => Dir::Right,
+        (b'L', Dir::Left) => Dir::Up,
+        (b'J', Dir::Down) => Dir::Left,
+        (b'J', Dir::Right) => Dir::Up,
+        (b'7', Dir::Right) => Dir::Down,
+        (b'7', Dir::Up) => Dir::Left,
+        (b'F', Dir::Up) => Dir::Right,
+        (b'F', Dir::Left) => Dir::Down,
+        _ => return None,
+    })
+}
+
+#[aoc_generator(day10)]
+pub fn generator(input: &str) -> (Vec<Vec<u8>>, (usize, usize)) {
+    let mut start = (0, 0);
+
+    let grid = input
+        .lines()
+        .enumerate()
+        .map(|(row, line)| {
+            line.bytes()
+                .enumerate()
+                .map(|(col, cell)| {
+                    if cell == b'S' {
+                        start = (row, col)
+                    }
+                    cell
+                })
+                .collect()
+        })
+        .collect();
+    (grid, start)
+}
+
+#[aoc(day10, part1)]
+pub fn part1((grid, start): &(Vec<Vec<u8>>, (usize, usize))) -> usize {
+    let (mut r, mut c) = *start;
+    let mut dir = Dir::Down; // assume we can go down first
+    let mut count = 0;
+
+    loop {
+        count += 1;
+
+        dir.next_pos(&mut r, &mut c);
+        let pipe = grid[r][c];
+        if pipe == b'S' {
+            break;
+        }
+        dir = next_direction(pipe, &dir)
+            .unwrap_or_else(|| panic!("Unknown pipe combination {} {:?}", char::from(pipe), dir,));
+    }
+
+    count / 2
+}
+
+#[aoc(day10, part2)]
+pub fn part2((grid, start): &(Vec<Vec<u8>>, (usize, usize))) -> usize {
+    let (mut r, mut c) = *start;
+    let mut dir = Dir::Down; // assume we can go down first
+    let mut pipe_set = HashSet::new();
+    pipe_set.insert((r, c));
+
+    loop {
+        dir.next_pos(&mut r, &mut c);
+        let pipe = grid[r][c];
+        if pipe == b'S' {
+            break;
+        }
+        pipe_set.insert((r, c));
+
+        dir = next_direction(pipe, &dir)
+            .unwrap_or_else(|| panic!("Unknown pipe combination {} {:?}", char::from(pipe), dir,));
+    }
+
+    let mut count = 0;
+    for (row, line) in grid.iter().enumerate() {
+        // we can as assume we're outside by default
+        let mut inside = false;
+        for (col, cell) in line.iter().enumerate() {
+            if pipe_set.contains(&(row, col)) {
+                // Check what parity we are in.
+                // If we see a vertical, then we go outside to inside and vice-versa
+                if b"|JLS".contains(cell) {
+                    inside = !inside;
+                }
+            } else {
+                count += usize::from(inside);
+            }
+        }
+    }
+    count
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE: &str = r"7-F7-
+.FJ|7
+SJLL7
+|F--J
+LJ.LJ";
+
+    const SAMPLE2: &str = r"FF7FSF7F7F7F7F7F---7
+L|LJ||||||||||||F--J
+FL-7LJLJ||||||LJL-77
+F--JF--7||LJLJ7F7FJ-
+L---JF-JLJ.||-FJLJJ7
+|F|F-JF---7F7-L7L|7|
+|FFJF7L7F-JF7|JL---7
+7-L-JL7||F7|L7F-7F7|
+L.L7LFJ|||||FJL7||LJ
+L7JLJL-JLJLJL--JLJ.L";
+
+    #[test]
+    pub fn input_test() {
+        println!("{:?}", generator(SAMPLE));
+
+        // assert_eq!(generator(SAMPLE), Object());
+    }
+
+    #[test]
+    pub fn part1_test() {
+        assert_eq!(part1(&generator(SAMPLE)), 8);
+    }
+
+    #[test]
+    pub fn part2_test() {
+        assert_eq!(part2(&generator(SAMPLE2)), 10);
+    }
+
+    mod regression {
+        use super::*;
+
+        const INPUT: &str = include_str!("../input/2023/day10.txt");
+        const ANSWERS: (usize, usize) = (6640, 411);
+
+        #[test]
+        pub fn test() {
+            let input = INPUT.trim_end_matches('\n');
+            let output = generator(input);
+
+            assert_eq!(part1(&output), ANSWERS.0);
+            assert_eq!(part2(&output), ANSWERS.1);
+        }
+    }
+}

src/lib.rs

@@ -10,5 +10,6 @@ pub mod day06;
 pub mod day07;
 pub mod day08;
 pub mod day09;
+pub mod day10;
 // Insert before
 aoc_lib! { year = 2023 }