day 10 - part 1

Cargo.toml

@@ -14,6 +14,7 @@ doctest = false
 test_lib = []
 
 [dependencies]
+itertools = "0.12.0"
 num = "0.4.1"
 pico-args = "0.5.0"
 prse = "1.1.0"

src/bin/10.rs

@@ -0,0 +1,162 @@
+use prse::{parse, Parse};
+use itertools::Itertools;
+advent_of_code::solution!(10);
+
+#[derive(Eq, PartialEq, Copy, Clone, Debug)]
+struct Tile {
+    i: usize,
+    j: usize,
+    tile_type: TileType
+}
+
+impl Tile {
+    fn adj(&self, tiles: &[Vec<Tile>], dir: Direction) -> Option<Self> {
+        let i = match dir {
+            Direction::Up => self.i.checked_sub(1)?,
+            Direction::Down => self.i.checked_add(1)?,
+            _ => self.i
+        };
+
+        let j = match dir {
+            Direction::Left => self.j.checked_sub(1)?,
+            Direction::Right => self.j.checked_add(1)?,
+            _ => self.j
+        };
+
+        tiles.get(i)?.get(j).cloned()
+    }
+}
+
+#[derive(Parse, Eq, PartialEq, Copy, Clone, Debug)]
+enum TileType {
+    #[prse = "|"]
+    Vertical,
+    #[prse = "-"]
+    Horizontal,
+    #[prse = "L"]
+    BendNE,
+    #[prse = "J"]
+    BendNW,
+    #[prse = "7"]
+    BendSW,
+    #[prse = "F"]
+    BendSE,
+    #[prse = "."]
+    Ground,
+    #[prse = "S"]
+    Start
+}
+
+#[derive(Eq, PartialEq, Copy, Clone, Debug)]
+enum Direction {
+    Up,
+    Down,
+    Left,
+    Right
+}
+
+#[derive(Eq, PartialEq, Debug)]
+struct Step {
+    tile: Tile,
+    dir: Direction
+}
+
+impl Step {
+    fn new(tile: Tile, dir: Direction) -> Self {
+        Self {
+            tile,
+            dir
+        }
+    }
+
+    fn from(&self, tiles: &[Vec<Tile>], dir: Direction) -> Option<Self> {
+        Some(Step::new(self.tile.adj(tiles, dir)?, dir))
+    }
+
+    // The Direction is where they're coming from
+    fn next(&self, tiles: &[Vec<Tile>]) -> Option<Step> {
+        let new_dir = match (self.tile.tile_type, self.dir) {
+
+            (TileType::Vertical, Direction::Down) => Direction::Down,
+            (TileType::BendNE, Direction::Down) => Direction::Right,
+            (TileType::BendNW, Direction::Down) => Direction::Left,
+
+            (TileType::Vertical, Direction::Up) => Direction::Up,
+            (TileType::BendSE, Direction::Up) => Direction::Right,
+            (TileType::BendSW, Direction::Up) => Direction::Left,
+
+            (TileType::Horizontal, Direction::Left) => Direction::Left,
+            (TileType::BendSE, Direction::Left) => Direction::Down,
+            (TileType::BendNE, Direction::Left) => Direction::Up,
+
+            (TileType::Horizontal, Direction::Right) => Direction::Right,
+            (TileType::BendSW, Direction::Right) => Direction::Down,
+            (TileType::BendNW, Direction::Right) => Direction::Up,
+
+            _ => { return None; }
+        };
+
+        self.from(tiles, new_dir)
+    }
+}
+
+fn parse_tiles(input: &str) -> Vec<Vec<Tile>> {
+    input.lines().enumerate().map(|(i, l)| {
+        l.chars().enumerate().map(|(j, t)| {
+            Tile { i, j, tile_type: parse!(t.to_string(), "{}")}
+        }).collect()
+    }).collect()
+}
+
+fn find_start(tiles: &[Vec<Tile>]) -> Option<Tile> {
+    for v in tiles {
+        for t in v {
+            if matches!(t.tile_type, TileType::Start) {
+                return Some(*t);
+            }
+        }
+    }
+
+    None
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let tiles = parse_tiles(input);
+    let start_tile = find_start(&tiles)?;
+
+    let mut cur_steps: Vec<Step> = [Direction::Up, Direction::Down, Direction::Left, Direction::Right]
+        .into_iter()
+        .filter_map(|dir| Some(Step::new(start_tile.adj(&tiles, dir)?, dir)))
+        .filter(|s| s.next(&tiles).is_some())
+        .collect();
+
+    let mut count = 1;
+
+    while !cur_steps.iter().map(|s| s.tile).all_equal() {
+        cur_steps = cur_steps.iter().map(|s| s.next(&tiles).unwrap()).collect();
+        count += 1;
+    }
+
+    Some(count)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(8));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}