day23

src/day15.rs

@@ -47,10 +47,10 @@ fn part2(input: &Vec<String>) -> usize {
             if let Some(position) = boxes[box_number].iter().position(|(l, _)| *l == *label) {
                 let _ = std::mem::replace(
                     &mut boxes[box_number][position],
-                    (label.clone().to_string(), *focal_length as usize),
+                    (label.to_string(), *focal_length as usize),
                 );
             } else {
-                boxes[box_number].push((label.clone().to_string(), *focal_length as usize));
+                boxes[box_number].push((label.to_string(), *focal_length as usize));
             }
         } else {
             panic!("invalid step AHHH {}", step)

src/day23.rs

@@ -0,0 +1,156 @@
+use std::collections::HashMap;
+
+use aoc_runner_derive::{aoc, aoc_generator};
+
+const NEIGHBORS: &[(i64,i64)] = &[(-1,0),(0,1),(1,0),(0,-1)];
+use itertools::Itertools;
+
+#[aoc_generator(day23)]
+fn parse(input: &str) -> Vec<Vec<char>> {
+    input.lines().map(|x| x.chars().collect::<Vec<_>>()).collect::<Vec<_>>()
+}
+
+fn dfs(graph: &HashMap<(usize,usize), Vec<(usize,usize,usize)>>, seen: &mut Vec<Vec<bool>>, (r,c): (usize, usize)) -> Option<usize> {
+    if r == seen.len() - 1 {
+        return Some(0);
+    }
+    let mut max_dist = None;
+    for &(rr, cc, d) in &graph[&(r,c)] {
+        if !seen[rr][cc] {
+            seen[rr][cc] = true;
+            if let Some(dist) = dfs(graph, seen, (rr,cc)) {
+                max_dist = Some(max_dist.unwrap_or(0).max(d+dist))
+            }
+            seen[rr][cc] = false;
+        }
+    }
+
+    max_dist
+}
+
+#[aoc(day23, part1)]
+fn part1(grid: &Vec<Vec<char>>) -> usize {
+    let mut graph = HashMap::<_,Vec<_>>::new();
+    for (r, c) in (0..grid.len()).cartesian_product(0..grid[0].len()) {
+        let neighbors = match grid[r][c] {
+            '#' => continue,
+            '.' => NEIGHBORS,
+            '^' => &NEIGHBORS[0..][..1],
+            '>' => &NEIGHBORS[1..][..1],
+            'v' => &NEIGHBORS[2..][..1],
+            '<' => &NEIGHBORS[3..][..1],
+            _ => unreachable!(),
+        };
+        let e = graph.entry((r,c)).or_default();
+
+        for (dr, dc) in neighbors {
+            let rr = (r as i64 + dr) as usize;
+            let cc = (c as i64 + dc) as usize;
+            if grid.get(rr).and_then(|row| row.get(cc)).is_some_and(|&t| t != '#') {
+                e.push((rr,cc,1));
+            }
+        }
+    }
+
+    let corridors = graph.iter()
+        .filter(|(_, n)| n.len() == 2)
+        .map(|(&node, _)| node)
+        .collect::<Vec<_>>();
+
+    for (r,c) in corridors {
+        let neighbors = graph.remove(&(r,c)).unwrap();
+        let (r1, c1, d1) = neighbors[0];
+        let (r2, c2, d2) = neighbors[1];
+        let n1 = graph.get_mut(&(r1,c1)).unwrap();
+        if let Some(i) = n1.iter().position(|&(rr,cc,_)| (rr,cc) == (r,c)) {
+            n1[i] = (r2,c2,d1+d2);
+        }
+        let n2 = graph.get_mut(&(r2,c2)).unwrap();
+        if let Some(i) = n2.iter().position(|&(rr,cc,_)| (rr,cc) == (r,c)) {
+            n2[i] = (r1,c1,d1+d2);
+        }
+    }
+
+    dfs(&graph, &mut vec![vec![false; grid[0].len()]; grid.len()], (0,1)).unwrap()
+}
+
+#[aoc(day23, part2)]
+fn part2(grid: &Vec<Vec<char>>) -> usize {
+    let mut graph = HashMap::<_,Vec<_>>::new();
+    for (r, c) in (0..grid.len()).cartesian_product(0..grid[0].len()) {
+        let neighbors = match grid[r][c] {
+            '#' => continue,
+            _ => NEIGHBORS,
+        };
+        let e = graph.entry((r,c)).or_default();
+
+        for (dr, dc) in neighbors {
+            let rr = (r as i64 + dr) as usize;
+            let cc = (c as i64 + dc) as usize;
+            if grid.get(rr).and_then(|row| row.get(cc)).is_some_and(|&t| t != '#') {
+                e.push((rr,cc,1));
+            }
+        }
+    }
+
+    let corridors = graph.iter()
+        .filter(|(_, n)| n.len() == 2)
+        .map(|(&node, _)| node)
+        .collect::<Vec<_>>();
+
+    for (r,c) in corridors {
+        let neighbors = graph.remove(&(r,c)).unwrap();
+        let (r1, c1, d1) = neighbors[0];
+        let (r2, c2, d2) = neighbors[1];
+        let n1 = graph.get_mut(&(r1,c1)).unwrap();
+        if let Some(i) = n1.iter().position(|&(rr,cc,_)| (rr,cc) == (r,c)) {
+            n1[i] = (r2,c2,d1+d2);
+        }
+        let n2 = graph.get_mut(&(r2,c2)).unwrap();
+        if let Some(i) = n2.iter().position(|&(rr,cc,_)| (rr,cc) == (r,c)) {
+            n2[i] = (r1,c1,d1+d2);
+        }
+    }
+
+    dfs(&graph, &mut vec![vec![false; grid[0].len()]; grid.len()], (0,1)).unwrap()
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EX: &str = r"#.#####################
+#.......#########...###
+#######.#########.#.###
+###.....#.>.>.###.#.###
+###v#####.#v#.###.#.###
+###.>...#.#.#.....#...#
+###v###.#.#.#########.#
+###...#.#.#.......#...#
+#####.#.#.#######.#.###
+#.....#.#.#.......#...#
+#.#####.#.#.#########v#
+#.#...#...#...###...>.#
+#.#.#v#######v###.###v#
+#...#.>.#...>.>.#.###.#
+#####v#.#.###v#.#.###.#
+#.....#...#...#.#.#...#
+#.#########.###.#.#.###
+#...###...#...#...#.###
+###.###.#.###v#####v###
+#...#...#.#.>.>.#.>.###
+#.###.###.#.###.#.#v###
+#.....###...###...#...#
+#####################.#";
+
+    #[test]
+    fn part1_example() {
+        assert_eq!(part1(&parse(EX)), 94);
+    }
+
+    #[test]
+    fn part2_example() {
+        assert_eq!(part2(&parse(EX)), 154);
+    }
+}

src/lib.rs

@@ -1,3 +1,4 @@
+mod day23;
 mod day22;
 mod day21;
 mod day20;