solution: day 25

data/examples/25.txt

@@ -0,0 +1,13 @@
+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

src/bin/25.rs

@@ -0,0 +1,80 @@
+use std::collections::HashMap;
+
+fn build_graph(input: &str, skips: &[(&str, &str)]) -> Vec<Vec<usize>> {
+    let mut nodes = Vec::new();
+    let mut mapper = HashMap::new();
+
+    for (node, neighs) in input.lines().filter_map(|x| x.split_once(": ")) {
+        if !mapper.contains_key(node) {
+            mapper.insert(node, nodes.len());
+            nodes.push(Vec::new());
+        }
+
+        let index_a = mapper[node];
+
+        for n in neighs.split(' ') {
+            if !mapper.contains_key(n) {
+                mapper.insert(n, nodes.len());
+                nodes.push(Vec::new());
+            }
+
+            if skips.contains(&(node, n)) || skips.contains(&(n, node)) {
+                continue;
+            }
+
+            let index_b = mapper[n];
+            nodes[index_a].push(index_b);
+            nodes[index_b].push(index_a);
+        }
+    }
+
+    nodes
+}
+
+pub fn part_one_wrapped(input: &str, skips: &[(&str, &str)]) -> Option<usize> {
+    let nodes = build_graph(input, skips);
+
+    let mut visited = vec![false; nodes.len()];
+    let mut stack = vec![0];
+
+    while let Some(node) = stack.pop() {
+        if visited[node] {
+            continue;
+        }
+        visited[node] = true;
+        for n in nodes[node].iter().copied() {
+            if !visited[n] {
+                stack.push(n);
+            }
+        }
+    }
+
+    let counter = visited.iter().copied().filter(|&x| x).count();
+    Some((nodes.len() - counter) * counter)
+}
+
+pub fn part_one(input: &str) -> Option<usize> {
+    // to figure out which nodes to skip
+    // echo "graph A {\n$(cat data/inputs/25.txt)\n}" | \
+    // sed 's/\(.*\): \(.*\)$/\1 -- {\2}/' | \
+    // dot -Tsvg -Kneato > graph.svg
+    let skips = [("sfm", "vmt"), ("vph", "mfc"), ("fql", "rmg")];
+    part_one_wrapped(input, &skips)
+}
+
+pub fn part_two(_input: &str) -> Option<String> {
+    Some("Happy chrismas!".into())
+}
+
+aoc::solution!(25);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        let skips = [("pzl", "hfx"), ("bvb", "cmg"), ("nvd", "jqt")];
+        let input = aoc::template::read_file("examples", 25);
+        assert_eq!(part_one_wrapped(&input, &skips), Some(54));
+    }
+}