Year 2024 Day 19

Author: maneatingape

README.md

@@ -90,6 +90,7 @@ Performance is reasonable even on older hardware, for example a 2011 MacBook Pro
 | 16 | [Reindeer Maze](https://adventofcode.com/2024/day/16) | [Source](src/year2024/day16.rs) | 390 |
 | 17 | [Chronospatial Computer](https://adventofcode.com/2024/day/17) | [Source](src/year2024/day17.rs) | 2 |
 | 18 | [RAM Run](https://adventofcode.com/2024/day/18) | [Source](src/year2024/day18.rs) | 42 |
+| 19 | [Linen Layout](https://adventofcode.com/2024/day/19) | [Source](src/year2024/day19.rs) | 425 |
 
 ## 2023
 

benches/benchmark.rs

@@ -88,5 +88,5 @@ benchmark!(year2023
 
 benchmark!(year2024
     day01, day02, day03, day04, day05, day06, day07, day08, day09, day10, day11, day12, day13,
-    day14, day15, day16, day17, day18
+    day14, day15, day16, day17, day18, day19
 );

src/lib.rs

@@ -68,5 +68,5 @@ library!(year2023 "Restore global snow production."
 
 library!(year2024 "Locate the Chief Historian in time for the big Christmas sleigh launch."
     day01, day02, day03, day04, day05, day06, day07, day08, day09, day10, day11, day12, day13,
-    day14, day15, day16, day17, day18
+    day14, day15, day16, day17, day18, day19
 );

src/main.rs

@@ -138,5 +138,5 @@ run!(year2023
 
 run!(year2024
     day01, day02, day03, day04, day05, day06, day07, day08, day09, day10, day11, day12, day13,
-    day14, day15, day16, day17, day18
+    day14, day15, day16, day17, day18, day19
 );

src/year2024/day19.rs

@@ -0,0 +1,80 @@
+//! # Linen Layout
+use crate::util::hash::*;
+
+pub fn parse(input: &str) -> Vec<u64> {
+    let (prefix, suffix) = input.split_once("\n\n").unwrap();
+
+    let mut trie = Vec::with_capacity(1_000);
+    trie.push(Node::new());
+
+    for towel in prefix.split(", ") {
+        let mut i = 0;
+
+        for j in towel.bytes().map(to_index) {
+            if trie[i].next[j] == 0 {
+                trie[i].next[j] = trie.len();
+                i = trie.len();
+                trie.push(Node::new());
+            } else {
+                i = trie[i].next[j];
+            }
+        }
+
+        trie[i].towel = true;
+    }
+
+    let seen = &mut FastMap::with_capacity(20_000);
+    suffix.lines().map(|design| helper(&trie, seen, design.as_bytes())).collect()
+}
+
+pub fn part1(input: &[u64]) -> usize {
+    input.iter().filter(|&&n| n > 0).count()
+}
+
+pub fn part2(input: &[u64]) -> u64 {
+    input.iter().sum()
+}
+
+fn helper<'a>(trie: &[Node], seen: &mut FastMap<&'a [u8], u64>, design: &'a [u8]) -> u64 {
+    if design.is_empty() {
+        return 1;
+    }
+    if let Some(&previous) = seen.get(design) {
+        return previous;
+    }
+
+    let mut i = 0;
+    let mut ways = 0;
+
+    for depth in 0..design.len() {
+        let j = to_index(design[depth]);
+        i = trie[i].next[j];
+
+        if i == 0 {
+            break;
+        }
+
+        if trie[i].towel {
+            ways += helper(trie, seen, &design[depth + 1..]);
+        }
+    }
+
+    seen.insert(design, ways);
+    ways
+}
+
+#[inline]
+fn to_index(b: u8) -> usize {
+    (b - b'a') as usize
+}
+
+struct Node {
+    towel: bool,
+    next: [usize; 26],
+}
+
+impl Node {
+    fn new() -> Self {
+        Node { towel: false, next: [0; 26] }
+    }
+}

tests/test.rs

@@ -81,5 +81,5 @@ test!(year2023
 
 test!(year2024
     day01, day02, day03, day04, day05, day06, day07, day08, day09, day10, day11, day12, day13,
-    day14, day15, day16, day17, day18
+    day14, day15, day16, day17, day18, day19
 );

tests/year2024/day19.rs

@@ -0,0 +1,25 @@
+use aoc::year2024::day19::*;
+
+const EXAMPLE: &str = "\
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 6);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 16);
+}