day 25

Cargo.lock

@@ -311,6 +311,14 @@ dependencies = [
  "z3",
 ]
 
+[[package]]
+name = "day-25"
+version = "0.0.0"
+dependencies = [
+ "indoc",
+ "pathfinding",
+]
+
 [[package]]
 name = "deprecate-until"
 version = "0.1.1"
@@ -581,9 +589,9 @@ checksum = "830b246a0e5f20af87141b25c173cd1b609bd7779a4617d6ec582abaf90870f3"
 
 [[package]]
 name = "pathfinding"
-version = "4.6.0"
+version = "4.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3ea07a6e677e47d6a84724d4fdf88b1e37fcb49ac94e236d7caeefd8fee75c8a"
+checksum = "f6f4a3f5089b981000cb50ec24320faf7a19649a45e8730e4adf49f78f066528"
 dependencies = [
  "deprecate-until",
  "fixedbitset",
@@ -726,18 +734,18 @@ dependencies = [
 
 [[package]]
 name = "thiserror"
-version = "1.0.50"
+version = "1.0.51"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f9a7210f5c9a7156bb50aa36aed4c95afb51df0df00713949448cf9e97d382d2"
+checksum = "f11c217e1416d6f036b870f14e0413d480dbf28edbee1f877abaf0206af43bb7"
 dependencies = [
  "thiserror-impl",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "1.0.50"
+version = "1.0.51"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "266b2e40bc00e5a6c09c3584011e08b06f123c00362c92b975ba9843aaaa14b8"
+checksum = "01742297787513b79cf8e29d1056ede1313e2420b7b3b15d0a768b4921f549df"
 dependencies = [
  "proc-macro2",
  "quote",

day-25/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "day-25"
+version = "0.0.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+pathfinding = "4.8.0"
+
+[dev-dependencies]
+indoc.workspace = true

day-25/src/main.rs

@@ -0,0 +1,127 @@
+use pathfinding::prelude::bfs;
+use std::collections::{HashMap, HashSet};
+
+/// Puzzle consists only of one part today.
+fn main() {
+    println!("{}", part1(include_str!("./input.txt")));
+}
+
+fn part1(input: &str) -> usize {
+    let mut graph = graph_from_input(input);
+
+    for i in 1..graph.len() {
+        let paths = (0..3)
+            .map(|_| {
+                let path = bfs(
+                    &0,
+                    |node| graph[node].iter().copied(),
+                    |&node| node == i as u16,
+                )
+                .unwrap();
+
+                // remove chosen edges
+                path.windows(2).for_each(|e| {
+                    graph.get_mut(&e[0]).unwrap().remove(&e[1]);
+                    graph.get_mut(&e[1]).unwrap().remove(&e[0]);
+                });
+
+                path
+            })
+            .collect::<Vec<_>>();
+
+        // check if graph is still connected
+        match bfs(
+            &0,
+            |node| graph[node].iter().copied(),
+            |&node| node == i as u16,
+        ) {
+            Some(_) => (),
+            None => {
+                let size_a = connected_count(&graph);
+                let size_b = graph.len() - size_a;
+
+                return size_a * size_b;
+            }
+        }
+
+        // restore edges
+        paths.into_iter().for_each(|path| {
+            path.windows(2).for_each(|e| {
+                graph.get_mut(&e[0]).unwrap().insert(e[1]);
+                graph.get_mut(&e[1]).unwrap().insert(e[0]);
+            });
+        });
+    }
+
+    0
+}
+
+type Graph = HashMap<u16, HashSet<u16>>;
+
+fn graph_from_input(input: &str) -> Graph {
+    let mut node_ids = HashMap::new();
+    let mut nodes = HashMap::new();
+    for line in input.lines() {
+        let (start, ends) = line.split_once(": ").unwrap();
+        for end in ends.split(' ') {
+            let id = node_ids.len() as u16;
+            node_ids.entry(end).or_insert(id);
+        }
+        let id = node_ids.len() as u16;
+        node_ids.entry(start).or_insert(id);
+
+        let start = node_ids[&start];
+        let ends = ends.split(' ').map(|e| node_ids[&e]);
+        for end in ends.clone() {
+            nodes.entry(end).or_insert_with(HashSet::new).insert(start);
+        }
+        nodes.entry(start).or_insert_with(HashSet::new).extend(ends);
+    }
+
+    nodes
+}
+
+fn connected_count(nodes: &Graph) -> usize {
+    let mut visited = HashSet::new();
+    let mut queue = Vec::new();
+    queue.push(*nodes.keys().next().unwrap());
+    while let Some(node) = queue.pop() {
+        if !visited.insert(node) {
+            continue;
+        }
+        for &neighbor in nodes[&node].iter() {
+            queue.push(neighbor);
+        }
+    }
+    visited.len()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(
+            part1(indoc!(
+                "
+                jqt: rhn xhk nvd
+                rsh: frs pzl lsr
+                xhk: hfx
+                cmg: qnr nvd lhk bvb
+                rhn: xhk bvb hfx
+                bvb: xhk hfx
+                pzl: lsr hfx nvd
+                qnr: nvd
+                ntq: jqt hfx bvb xhk
+                nvd: lhk
+                lsr: lhk
+                rzs: qnr cmg lsr rsh
+                frs: qnr lhk lsr
+                "
+            )),
+            54
+        );
+    }
+}