solution: day 21

Cargo.lock

@@ -17,6 +17,18 @@ version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
+[[package]]
+name = "ahash"
+version = "0.8.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e89da841a80418a9b391ebaea17f5c112ffaaa96f621d2c285b5174da76b9011"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+ "version_check",
+ "zerocopy",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "1.1.3"
@@ -36,6 +48,7 @@ checksum = "683d7910e743518b0e34f1186f92494becacb047c7b6bf616c96772180fef923"
 name = "aoc"
 version = "48.0.0"
 dependencies = [
+ "cached",
  "hashbrown 0.15.2",
  "itertools",
  "num-integer",
@@ -87,6 +100,39 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dfb24e866b15a1af2a1b663f10c6b6b8f397a84aadb828f12e5b289ec23a3a3c"
 
+[[package]]
+name = "cached"
+version = "0.54.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9718806c4a2fe9e8a56fd736f97b340dd10ed1be8ed733ed50449f351dc33cae"
+dependencies = [
+ "ahash",
+ "cached_proc_macro",
+ "cached_proc_macro_types",
+ "hashbrown 0.14.5",
+ "once_cell",
+ "thiserror",
+ "web-time",
+]
+
+[[package]]
+name = "cached_proc_macro"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f42a145ed2d10dce2191e1dcf30cfccfea9026660e143662ba5eec4017d5daa"
+dependencies = [
+ "darling",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.90",
+]
+
+[[package]]
+name = "cached_proc_macro_types"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ade8366b8bd5ba243f0a58f036cc0ca8a2f069cff1a2351ef1cac6b083e16fc0"
+
 [[package]]
 name = "cc"
 version = "1.0.78"
@@ -115,6 +161,41 @@ version = "0.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5827cebf4670468b8772dd191856768aedcb1b0278a04f989f7766351917b9dc"
 
+[[package]]
+name = "darling"
+version = "0.20.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f63b86c8a8826a49b8c21f08a2d07338eec8d900540f8630dc76284be802989"
+dependencies = [
+ "darling_core",
+ "darling_macro",
+]
+
+[[package]]
+name = "darling_core"
+version = "0.20.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95133861a8032aaea082871032f5815eb9e98cef03fa916ab4500513994df9e5"
+dependencies = [
+ "fnv",
+ "ident_case",
+ "proc-macro2",
+ "quote",
+ "strsim",
+ "syn 2.0.90",
+]
+
+[[package]]
+name = "darling_macro"
+version = "0.20.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d336a2a514f6ccccaa3e09b02d41d35330c07ddf03a62165fcec10bb561c7806"
+dependencies = [
+ "darling_core",
+ "quote",
+ "syn 2.0.90",
+]
+
 [[package]]
 name = "dotenvy"
 version = "0.15.6"
@@ -275,6 +356,16 @@ version = "0.12.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
 
+[[package]]
+name = "hashbrown"
+version = "0.14.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5274423e17b7c9fc20b6e7e208532f9b19825d82dfd615708b70edd83df41f1"
+dependencies = [
+ "ahash",
+ "allocator-api2",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.15.2"
@@ -366,6 +457,12 @@ dependencies = [
  "tokio-native-tls",
 ]
 
+[[package]]
+name = "ident_case"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9e0384b61958566e926dc50660321d12159025e767c18e043daf26b70104c39"
+
 [[package]]
 name = "idna"
 version = "0.3.0"
@@ -535,9 +632,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.16.0"
+version = "1.20.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "86f0b0d4bf799edbc74508c1e8bf170ff5f41238e5f8225603ca7caaae2b7860"
+checksum = "1261fe7e33c73b354eab43b1273a57c8f967d0391e80353e51f764ac02cf6775"
 
 [[package]]
 name = "openssl"
@@ -562,7 +659,7 @@ checksum = "b501e44f11665960c7e7fcf062c7d96a14ade4aa98116c004b2e37b5be7d736c"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 1.0.107",
 ]
 
 [[package]]
@@ -616,18 +713,18 @@ checksum = "6ac9a59f73473f1b8d852421e59e64809f025994837ef743615c6d0c5b305160"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.69"
+version = "1.0.92"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "134c189feb4956b20f6f547d2cf727d4c0fe06722b20a0eec87ed445a97f92da"
+checksum = "37d3544b3f2748c54e147655edb5025752e2303145b5aefb3c3ea2c78b973bb0"
 dependencies = [
  "unicode-ident",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.33"
+version = "1.0.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5267fca4496028628a95160fc423a33e8b2e6af8a5302579e322e4b520293cae"
+checksum = "b5b9d34b8991d19d98081b46eacdd8eb58c6f2b201139f7c5f643cc155a633af"
 dependencies = [
  "proc-macro2",
 ]
@@ -829,6 +926,12 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
+
 [[package]]
 name = "syn"
 version = "1.0.107"
@@ -840,6 +943,17 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "syn"
+version = "2.0.90"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "919d3b74a5dd0ccd15aeb8f93e7006bd9e14c295087c9896a110f490752bcf31"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
 [[package]]
 name = "system-configuration"
 version = "0.5.1"
@@ -875,6 +989,26 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6aaf5339b578ea85b50e080feb250a3e8ae8cfcdff9a461c9ec2904bc923f52"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fee6c4efc90059e10f81e6d42c60a18f76588c3d74cb83a0b242a2b6c7504c1"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.90",
+]
+
 [[package]]
 name = "tinyvec"
 version = "1.6.0"
@@ -1000,6 +1134,12 @@ version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "accd4ea62f7bb7a82fe23066fb0957d48ef677f6eeb8215f372f52e48bb32426"
 
+[[package]]
+name = "version_check"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
+
 [[package]]
 name = "want"
 version = "0.3.0"
@@ -1037,7 +1177,7 @@ dependencies = [
  "once_cell",
  "proc-macro2",
  "quote",
- "syn",
+ "syn 1.0.107",
  "wasm-bindgen-shared",
 ]
 
@@ -1071,7 +1211,7 @@ checksum = "07bc0c051dc5f23e307b13285f9d75df86bfdf816c5721e573dec1f9b8aa193c"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn",
+ "syn 1.0.107",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
@@ -1092,6 +1232,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "web-time"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a6580f308b1fad9207618087a65c04e7a10bc77e02c8e84e9b00dd4b12fa0bb"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "winapi"
 version = "0.3.9"
@@ -1232,3 +1382,23 @@ dependencies = [
  "cfg-if",
  "windows-sys 0.48.0",
 ]
+
+[[package]]
+name = "zerocopy"
+version = "0.7.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1b9b4fd18abc82b8136838da5d50bae7bdea537c574d8dc1a34ed098d6c166f0"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.7.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fa4f8080344d4671fb4e831a13ad1e68092748387dfc4f55e356242fae12ce3e"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.90",
+]

Cargo.toml

@@ -21,6 +21,7 @@ authors.workspace = true
 repository.workspace = true
 
 [dependencies]
+cached = "0.54.0"
 hashbrown = "0.15.2"
 itertools = "0.13.0"
 num-integer = "0.1.46"

data/examples/20.txt

@@ -0,0 +1,15 @@
+###############
+#...#...#.....#
+#.#.#.#.#.###.#
+#S#...#.#.#...#
+#######.#.#.###
+#######.#.#...#
+#######.#.###.#
+###..E#...#...#
+###.#######.###
+#...###...#...#
+#.#####.#.###.#
+#.#...#.#.#...#
+#.#.#.#.#.#.###
+#...#...#...###
+###############

data/examples/21.txt

@@ -0,0 +1,5 @@
+029A
+980A
+179A
+456A
+379A

src/bin/20.rs

@@ -0,0 +1,135 @@
+use std::collections::VecDeque;
+
+use aoc::grid_vec::{Direction, Grid, Point};
+use hashbrown::HashMap;
+
+fn parse_input(input: &str) -> (Grid, Point, Point) {
+    let mut grid: Grid = input.parse().unwrap();
+    let start = grid.find(b'S').unwrap();
+    let end = grid.find(b'E').unwrap();
+
+    grid[start] = b'.';
+    grid[end] = b'.';
+
+    (grid, start, end)
+}
+fn bfs(
+    grid: &Grid,
+    start: Point,
+    limit: Option<usize>,
+    cheat: bool,
+    visited: &mut HashMap<Point, usize>,
+    queue: &mut VecDeque<(Point, usize)>,
+) {
+    visited.clear();
+    queue.clear();
+
+    queue.push_back((start, 0));
+
+    while let Some((p, l)) = queue.pop_front() {
+        if visited.contains_key(&p) {
+            continue;
+        }
+        visited.insert(p, l);
+
+        for d in Direction::CROSS {
+            let n = p + d;
+
+            let nv = grid.get(&n);
+            let uwnv = *nv.unwrap_or(&b'#');
+            let valid_neigh = (cheat && nv.is_some()) || uwnv == b'.';
+            let valid_length = l < limit.unwrap_or(usize::MAX);
+            let unvisited = !visited.contains_key(&n);
+
+            if valid_neigh && valid_length && unvisited {
+                queue.push_back((n, l + 1));
+            }
+        }
+    }
+}
+
+fn get_cheat_neighbours_and_benchmark(
+    grid: &Grid,
+    start: Point,
+    cheat_limit: usize,
+) -> HashMap<Point, Vec<(Point, usize)>> {
+    let mut map = HashMap::<Point, Vec<(Point, usize)>>::new();
+
+    let mut reuse_queue = VecDeque::new();
+    let mut reuse_visited = HashMap::new();
+
+    let mut valid_points = HashMap::new();
+
+    bfs(
+        grid,
+        start,
+        None,
+        false,
+        &mut valid_points,
+        &mut reuse_queue,
+    );
+
+    for (&s, _) in valid_points.iter() {
+        bfs(
+            grid,
+            s,
+            Some(cheat_limit),
+            true,
+            &mut reuse_visited,
+            &mut reuse_queue,
+        );
+        for (&point, &length) in reuse_visited.iter().filter(|(&p, _)| grid[p] == b'.') {
+            map.entry(s).or_default().push((point, length));
+        }
+    }
+
+    map
+}
+
+fn cheated_bfs(
+    grid: &Grid,
+    start: Point,
+    end: Point,
+    cheat_limit: usize,
+    increase_limit: usize,
+) -> usize {
+    let neighbours = get_cheat_neighbours_and_benchmark(grid, start, cheat_limit);
+
+    let mut reuse_queue = VecDeque::new();
+
+    let mut from_start = HashMap::new();
+    let mut from_end = HashMap::new();
+
+    bfs(grid, start, None, false, &mut from_start, &mut reuse_queue);
+    bfs(grid, end, None, false, &mut from_end, &mut reuse_queue);
+
+    let benchmark = from_start[&end];
+
+    let mut count = 0;
+
+    for node in from_start.keys() {
+        for (neigh, cheat_dist) in neighbours[node].iter() {
+            let start_dist = from_start[node];
+            let end_dist = from_end[neigh];
+
+            let dist = start_dist + cheat_dist + end_dist;
+            if dist < benchmark && dist.abs_diff(benchmark) >= increase_limit {
+                count += 1;
+            }
+        }
+    }
+
+    count
+}
+
+pub fn part_one(input: &str) -> Option<usize> {
+    let (grid, start, end) = parse_input(input);
+    cheated_bfs(&grid, start, end, 2, 100).into()
+}
+
+pub fn part_two(input: &str) -> Option<usize> {
+    let (grid, start, end) = parse_input(input);
+    cheated_bfs(&grid, start, end, 20, 100).into()
+}
+
+aoc::solution!(20);

src/bin/21.rs

@@ -0,0 +1,157 @@
+use std::collections::VecDeque;
+
+use hashbrown::HashMap;
+use itertools::Itertools;
+
+use cached::proc_macro::cached;
+use cached::SizedCache;
+
+#[rustfmt::skip]
+#[allow(clippy::type_complexity)]
+const NUMPAD: [(u8, [Option<(u8, u8)>; 4]); 11] = [
+    (b'0', [Some((b'2', b'^')), Some((b'A', b'>')), None, None]),
+    (b'1', [Some((b'2', b'>')), Some((b'4', b'^')), None, None]),
+    (b'2', [Some((b'0', b'v')), Some((b'1', b'<')), Some((b'3', b'>')), Some((b'5', b'^')),]), 
+    (b'3', [Some((b'2', b'<')), Some((b'6', b'^')), Some((b'A', b'v')), None,]), 
+    (b'4', [Some((b'1', b'v')), Some((b'5', b'>')), Some((b'7', b'^')), None,]), 
+    (b'5', [Some((b'2', b'v')), Some((b'4', b'<')), Some((b'6', b'>')), Some((b'8', b'^')),]), 
+    (b'6', [Some((b'3', b'v')), Some((b'5', b'<')), Some((b'9', b'^')), None,]), 
+    (b'7', [Some((b'4', b'v')), Some((b'8', b'>')), None, None]), 
+    (b'8', [Some((b'5', b'v')), Some((b'7', b'<')), Some((b'9', b'>')), None,]), 
+    (b'9', [Some((b'6', b'v')), Some((b'8', b'<')), None, None]),
+    (b'A', [Some((b'0', b'<')), Some((b'3', b'^')), None, None]),
+];
+
+#[rustfmt::skip]
+#[allow(clippy::type_complexity)]
+const KEYPAD: [(u8, [Option<(u8, u8)>; 3]); 5] = [
+    (b'^', [Some((b'A', b'>')), Some((b'v', b'v')), None]),
+    (b'<', [Some((b'v', b'>')), None, None]),
+    (b'v', [Some((b'<', b'<')), Some((b'^', b'^')), Some((b'>', b'>'))]),
+    (b'>', [Some((b'v', b'<')), Some((b'A', b'^')), None]),
+    (b'A', [Some((b'^', b'<')), Some((b'>', b'v')), None]),
+];
+
+fn bfs(graph: &HashMap<u8, Vec<(u8, u8)>>, s: u8, e: u8) -> Vec<VecDeque<u8>> {
+    let mut res = Vec::new();
+
+    let mut queue = VecDeque::new();
+    let mut shortest = usize::MAX;
+
+    queue.push_back((s, VecDeque::new()));
+
+    while let Some((n, mut p)) = queue.pop_front() {
+        if n == e {
+            if shortest == usize::MAX {
+                shortest = p.len();
+            }
+
+            if p.len() == shortest {
+                p.push_back(b'A');
+                res.push(p);
+            }
+            continue;
+        }
+
+        if p.len() >= shortest {
+            continue;
+        }
+
+        for (nn, c) in graph[&n].iter().copied() {
+            let mut np = p.clone();
+            np.push_back(c);
+
+            queue.push_back((nn, np));
+        }
+    }
+
+    res
+}
+
+#[cached(
+    ty = "SizedCache<String, usize>",
+    create = "{ SizedCache::with_size(100000) }",
+    convert = r#"{ format!("{sequence:?}{level}{graph}") }"#
+)]
+fn dfs(
+    graphs: &[HashMap<u8, Vec<(u8, u8)>>],
+    graph: usize,
+    mut sequence: VecDeque<u8>,
+    level: usize,
+) -> usize {
+    let graph = &graphs[graph];
+    sequence.push_front(b'A');
+    let mut res = 0;
+
+    for (n1, n2) in sequence.into_iter().tuple_windows() {
+        let paths = bfs(graph, n1, n2);
+        if level == 0 {
+            res += paths.into_iter().map(|p| p.len()).min().unwrap();
+        } else {
+            res += paths
+                .into_iter()
+                .map(|p| dfs(graphs, 1, p, level - 1))
+                .min()
+                .unwrap();
+        }
+    }
+
+    res
+}
+
+fn build_graphs() -> [HashMap<u8, Vec<(u8, u8)>>; 2] {
+    let mut numpad = HashMap::new();
+    for (k, v) in NUMPAD.iter() {
+        numpad.insert(*k, v.iter().filter_map(|&x| x).collect_vec());
+    }
+
+    let mut keypad = HashMap::new();
+    for (k, v) in KEYPAD.iter() {
+        keypad.insert(*k, v.iter().filter_map(|&x| x).collect_vec());
+    }
+
+    [numpad, keypad]
+}
+
+fn solve_chain(input: &str, level: usize) -> usize {
+    let graphs = build_graphs();
+
+    let mut res = 0;
+    for line in input.lines() {
+        let n: usize = line.strip_suffix("A").unwrap().parse().unwrap();
+        let sequence = VecDeque::from_iter(line.as_bytes().iter().copied());
+        let min_len = dfs(&graphs, 0, sequence, level);
+        res += min_len * n;
+    }
+
+    res
+}
+
+pub fn part_one(input: &str) -> Option<usize> {
+    Some(solve_chain(input, 2))
+}
+
+pub fn part_two(input: &str) -> Option<usize> {
+    Some(solve_chain(input, 25))
+}
+
+aoc::solution!(21);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(
+            part_one(&aoc::template::read_file("examples", 21)),
+            Some(126384)
+        );
+    }
+    #[test]
+    fn test_part_two() {
+        assert_eq!(
+            part_two(&aoc::template::read_file("examples", 21)),
+            Some(154115708116294)
+        );
+    }
+}