Solve day 16

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+#.#.#.###.#.#.#.#######.###.#.#######.#.#.#.#####.#.#.#.#.###.#####.###.#.#.#########.#.#######.#.#####.#.###.#.#.#####.#.#.###.#######.#.#.#
+#.#...#.....#.#.....#...#...#.........#.#...#.....#...#...#...........................#...#...#.#.#...#.....#.#.....#...#.#...#.....#...#.#.#
+#.###.#.#.###.#.###.#.###.#.#########.#.#.###.#####.#####.#.#.#.###.#.#.###.#.#######.###.#.###.#.#.#.###.#.#.#.###.#.#.#.###.#####.#.###.#.#
+#...#.#.....#.#...#.#.#...#.#...#...#.#...#.......#...#.#...#.#.#...#.#...#.#.....#...#...#.....#...#...#.....#.#...#.#.....#.....#.#.#.....#
+#.#.#.###.#.#.#.#.#.###.###.#.#.#.#.#.###.#######.#.#.#.#.#.#.#.#.#######.#.#####.#.#.#.###.#####.#####.#.#####.#.#.#.#.#######.#.#.#.#.###.#
+#.#.#.....#.#...#.#.....#.#.#.#...#.#...#...#.....#...#...#...#.#.......#.......#.#.#...#...#.........#.....#...#.#...#.#.....#.#.#.#.....#.#
+#.#.#####.#.#.#.#.#######.#.#.#####.#####.#.#.#####.###.#.#.###.#######.#.#.#####.#.#.###.###########.#####.#.#.###.#.#.#.###.###.#.###.#.#.#
+#.#.#...#.#.#.#.#...#.......#.....#.......#.#.#.....#...#.#.......#...#...#.#...........................#...#.#.....#...#...#.#...#.......#.#
+###.#.#.#.#.#.#.###.###########.#.#####.#.#.#.#.#.#.###.#.#.#####.#.#.###.###.#####.###.#.#.###.#.#.###.#.###.#.###.#.#####.#.#.#######.###.#
+#...#.#.....#.#...#.#...........#.#...#.....#.#.#.#...#.........................#.#.#...#...#...#.#.....#.#.....#...........#.#...#.#...#...#
+#.#.#.###.#####.#.#.#.#######.###.#.#########.#.###.#.###.#.#####.#.#.###.#.#.#.#.#.#.#######.#########.#.###.###.#.#.#######.###.#.#.#.#.###
+#.#.#.#...#.....#.#.#.#.....#.#...#...........#...#.........................#.#.#...#.#.#...#.#.............#...#.......#...#.....#...#.....#
+#.###.#.#.#.#####.#.#.#####.#.#.###########.###.#.#.###.#.#.###.###.#.#.#.#.###.#.###.#.#.#.#.#.#.#.#.#####.###.###.#.#.#.#.#######.###.#.#.#
+#S......#...#.....#.........#...............#...#.....#.......#.....#...#.......#.....#...#.....#...#.......#...........#.#.................#
+#############################################################################################################################################

src/bin/16.rs

@@ -0,0 +1,136 @@
+use std::{
+    cmp::Reverse,
+    collections::{hash_map::Entry, BinaryHeap, HashMap, HashSet},
+};
+
+static DIRECTIONS: [(isize, isize); 4] = [(0, -1), (1, 0), (0, 1), (-1, 0)];
+
+fn walk_paths(
+    visited: &Visited,
+    x: usize,
+    y: usize,
+    dir: usize,
+    tiles: &mut HashSet<(usize, usize)>,
+) {
+    if let Some((_, v)) = visited.get(&(x, y, dir)) {
+        for &(nx, ny, ndir) in v {
+            tiles.insert((nx, ny));
+
+            walk_paths(visited, nx, ny, ndir, tiles);
+        }
+    }
+}
+
+type Visited = HashMap<(usize, usize, usize), (i32, HashSet<(usize, usize, usize)>)>;
+
+fn main() {
+    let text = std::fs::read_to_string("input/16-1.in").unwrap();
+
+    let mut startx = 0;
+    let mut starty = 0;
+    let start_dir = 1;
+    let mut endx = 0;
+    let mut endy = 0;
+
+    let map = text
+        .lines()
+        .enumerate()
+        .map(|(y, l)| {
+            l.chars()
+                .enumerate()
+                .map(move |(x, c)| (x, y, c))
+                .map(|(x, y, c)| match c {
+                    '#' => false,
+                    '.' => true,
+                    'S' => {
+                        startx = x;
+                        starty = y;
+                        true
+                    }
+                    'E' => {
+                        endx = x;
+                        endy = y;
+                        true
+                    }
+                    _ => unreachable!(),
+                })
+                .collect::<Vec<_>>()
+        })
+        .collect::<Vec<_>>();
+
+    let mut queue = BinaryHeap::new();
+    let mut visited = HashSet::new();
+
+    queue.push(Reverse((0, startx, starty, start_dir)));
+
+    let mut final_score = 0;
+    while let Some(Reverse((score, x, y, dir))) = queue.pop() {
+        if x == endx && y == endy {
+            final_score = score;
+            break;
+        }
+
+        if visited.insert((x, y, dir)) {
+            let (dx, dy) = DIRECTIONS[dir];
+            let nextx = x.checked_add_signed(dx).unwrap();
+            let nexty = y.checked_add_signed(dy).unwrap();
+            if map[nexty][nextx] {
+                queue.push(Reverse((score + 1, nextx, nexty, dir)));
+            }
+
+            queue.push(Reverse((score + 1000, x, y, (dir + 1) % 4)));
+            queue.push(Reverse((score + 1000, x, y, (dir + 3) % 4)));
+        }
+    }
+
+    println!("{final_score}");
+
+    let mut queue = BinaryHeap::new();
+    let mut visited: Visited = HashMap::new();
+
+    queue.push(Reverse((0, (startx, starty, start_dir), (0, 0, 0))));
+
+    while let Some(Reverse((score, pos, from))) = queue.pop() {
+        match visited.entry(pos) {
+            Entry::Occupied(mut occupied_entry) => {
+                if score > occupied_entry.get().0 {
+                    continue;
+                } else {
+                    occupied_entry.get_mut().1.insert(from);
+                }
+            }
+            Entry::Vacant(vacant_entry) => {
+                vacant_entry.insert((score, HashSet::from([from])));
+            }
+        };
+        // if visited.insert((x, y, dir)) {
+        let (x, y, dir) = pos;
+        let (dx, dy) = DIRECTIONS[dir];
+        let nextx = x.checked_add_signed(dx).unwrap();
+        let nexty = y.checked_add_signed(dy).unwrap();
+        if map[nexty][nextx] {
+            queue.push(Reverse((score + 1, (nextx, nexty, dir), pos)));
+        }
+
+        queue.push(Reverse((score + 1000, (x, y, (dir + 1) % 4), pos)));
+        queue.push(Reverse((score + 1000, (x, y, (dir + 3) % 4), pos)));
+        // }
+    }
+
+    let mut tiles = HashSet::new();
+
+    if visited.get(&(endx, endy, 0)).unwrap().0 == final_score {
+        walk_paths(&visited, endx, endy, 0, &mut tiles);
+    }
+    if visited.get(&(endx, endy, 1)).unwrap().0 == final_score {
+        walk_paths(&visited, endx, endy, 1, &mut tiles);
+    }
+    if visited.get(&(endx, endy, 2)).unwrap().0 == final_score {
+        walk_paths(&visited, endx, endy, 2, &mut tiles);
+    }
+    if visited.get(&(endx, endy, 3)).unwrap().0 == final_score {
+        walk_paths(&visited, endx, endy, 3, &mut tiles);
+    }
+
+    println!("{}", tiles.len());
+}