Day 23

Author: prevostc

Cargo.lock

@@ -33,6 +33,7 @@ mygrid = { version = "0.0.1", path = "mygrid" }
 nalgebra = "0.33.2"
 num = "0.4.3"
 object-pool = "0.6.0"
+petgraph = "0.6.5"
 phf = { version = "0.11.2", features = ["macros"] }
 pico-args = "0.5.0"
 rayon = "1.10.0"

Cargo.toml

@@ -33,8 +33,9 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 20](./src/bin/20.rs) | `308.3µs` | `1.8ms` |
 | [Day 21](./src/bin/21.rs) | `10.9µs` | `112.6µs` |
 | [Day 22](./src/bin/22.rs) | `610.4µs` | `9.0s` |
+| [Day 23](./src/bin/23.rs) | `157.2µs` | `620.5µs` |
 
-**Total: 9017.30ms**
+**Total: 9018.08ms**
 <!--- benchmarking table --->
 
 ---

README.md

@@ -0,0 +1,32 @@
+kh-tc
+qp-kh
+de-cg
+ka-co
+yn-aq
+qp-ub
+cg-tb
+vc-aq
+tb-ka
+wh-tc
+yn-cg
+kh-ub
+ta-co
+de-co
+tc-td
+tb-wq
+wh-td
+ta-ka
+td-qp
+aq-cg
+wq-ub
+ub-vc
+de-ta
+wq-aq
+wq-vc
+wh-yn
+ka-de
+kh-ta
+co-tc
+wh-qp
+tb-vc
+td-yn

data/examples/23.txt

@@ -0,0 +1,91 @@
+use itertools::Itertools;
+use rayon::iter::{IntoParallelRefMutIterator, ParallelIterator};
+use rustc_hash::{FxHashMap, FxHashSet};
+
+advent_of_code::solution!(23);
+
+type Node = (u8, u8);
+type Connections = FxHashMap<Node, FxHashSet<Node>>;
+
+fn parse_input(input: &str) -> Connections {
+    let mut connections = FxHashMap::default();
+
+    // nice technique from https://github.com/ndunnett/aoc/blob/main/rust/2024/src/bin/day23.rs
+    for (a0, a1, _, b0, b1, _) in input.bytes().tuples() {
+        connections
+            .entry((a0, a1))
+            .or_insert(FxHashSet::default())
+            .insert((b0, b1));
+
+        connections
+            .entry((b0, b1))
+            .or_insert(FxHashSet::default())
+            .insert((a0, a1));
+    }
+
+    connections
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let graph = parse_input(input);
+
+    type Island = (Node, Node, Node);
+
+    let all_islands = graph
+        .iter()
+        .filter(|(l1, _)| l1.0 == b't')
+        .flat_map(|(a, adj_a)| {
+            adj_a.iter().flat_map(|b| {
+                adj_a.intersection(&graph[b]).map(|c| {
+                    let mut island = [*a, *b, *c];
+                    island.sort();
+                    island.into_iter().next_tuple::<Island>().unwrap()
+                })
+            })
+        });
+
+    let islands = FxHashSet::from_iter(all_islands);
+    Some(islands.len() as u32)
+}
+
+pub fn part_two(input: &str) -> Option<String> {
+    let graph = parse_input(input);
+    let mut cliques = graph
+        .keys()
+        .map(|&a| FxHashSet::from_iter([a]))
+        .collect::<Vec<_>>();
+
+    cliques.par_iter_mut().for_each(|clique| {
+        graph.keys().for_each(|a| {
+            if clique.iter().all(|b| graph[a].contains(b)) {
+                clique.insert(*a);
+            }
+        });
+    });
+
+    let max_clique = cliques.iter().max_by(|a, b| a.len().cmp(&b.len())).unwrap();
+    let password = max_clique
+        .iter()
+        .sorted()
+        .map(|node| format!("{}{}", node.0 as char, node.1 as char))
+        .join(",");
+
+    Some(password)
+}
+
+#[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(7));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some("co,de,ka,ta".to_string()));
+    }
+}