141 lines
3.2 KiB
Rust
141 lines
3.2 KiB
Rust
use std::collections::HashMap;
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use anyhow::Result;
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use aoc_runner_derive::aoc;
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fn search(node: &str, nodes: &HashMap<&str, Vec<&str>>, path: String, paths: &mut Vec<String>) {
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if node == "end" {
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paths.push(path);
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return;
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}
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for neighbor in &nodes[node] {
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// If lowercase.
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if neighbor.as_bytes()[0] & 0x20 != 0 && path.contains(neighbor) {
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continue;
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}
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search(neighbor, nodes, format!("{},{}", path, neighbor), paths);
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}
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}
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fn paths(nodes: &HashMap<&str, Vec<&str>>) -> usize {
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let mut paths = Vec::new();
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search("start", nodes, "start".to_string(), &mut paths);
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paths.len()
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}
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#[aoc(day12, part1)]
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fn part1(input: &str) -> Result<usize> {
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let mut nodes = HashMap::new();
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input.lines().for_each(|p| {
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let (n1, n2) = p.split_once('-').expect("missing dash");
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nodes.entry(n1).or_insert_with(Vec::new).push(n2);
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nodes.entry(n2).or_insert_with(Vec::new).push(n1);
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});
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Ok(paths(&nodes))
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}
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fn search2<'a>(
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node: &str,
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nodes: &HashMap<&'a str, Vec<&'a str>>,
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path: &[&'a str],
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paths: &mut Vec<Vec<&'a str>>,
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double: &'a str,
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smalls: &[&'a str],
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) {
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if node == "end" {
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paths.push(path.to_vec());
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return;
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}
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for neighbor in &nodes[node] {
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// If lowercase.
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if neighbor.as_bytes()[0] & 0x20 != 0 {
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if neighbor == &double {
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// Allow two passes for this small node.
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if path.iter().filter(|p| p == &neighbor).count() >= 2 {
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continue;
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}
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} else {
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// Only allow one pass for this small node.
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if path.contains(neighbor) {
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continue;
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}
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}
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}
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let mut child_path = path.to_vec();
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child_path.push(neighbor);
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search2(neighbor, nodes, &child_path, paths, double, smalls);
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}
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}
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fn paths2(nodes: &HashMap<&str, Vec<&str>>) -> usize {
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let mut paths = Vec::new();
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let smalls: Vec<_> = nodes
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.keys()
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.filter(|n| n.as_bytes()[0] & 0x20 != 0)
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.filter(|&n| n != &"start" && n != &"end")
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.cloned()
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.collect();
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for double in &smalls {
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search2(
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"start",
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nodes,
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&["start"],
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&mut paths,
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double,
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smalls.as_slice(),
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);
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}
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paths.sort();
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paths.dedup();
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paths.len()
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}
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#[aoc(day12, part2)]
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fn part2(input: &str) -> Result<usize> {
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let mut nodes = HashMap::new();
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input.lines().for_each(|p| {
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let (n1, n2) = p.split_once('-').expect("missing dash");
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nodes.entry(n1).or_insert_with(Vec::new).push(n2);
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nodes.entry(n2).or_insert_with(Vec::new).push(n1);
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});
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Ok(paths2(&nodes))
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_part1() -> Result<()> {
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let input = r#"
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start-A
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start-b
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A-c
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A-b
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b-d
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A-end
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b-end
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"#
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.trim();
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assert_eq!(part1(input)?, 10);
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Ok(())
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}
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#[test]
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fn test_part2() -> Result<()> {
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let input = r#"
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start-A
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start-b
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A-c
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A-b
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b-d
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A-end
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b-end
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"#
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.trim();
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assert_eq!(part2(input)?, 36);
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Ok(())
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}
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}
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