Solve 19

src/bin/19.rs

@@ -0,0 +1,50 @@
+use aoc::*;
+use cached::proc_macro::cached;
+use cached::UnboundCache;
+
+const INPUT: &str = include_str!("../../input/19");
+
+fn main() {
+    assert_example!(part1, "19-test", 6);
+    println!("Part 1: {}", part1(INPUT));
+    assert_example!(part2, "19-test", 16);
+    println!("Part 2: {}", part2(INPUT));
+}
+
+fn part1(input: &str) -> usize {
+    let (available, requested) = parse(input);
+    requested
+        .filter(|requested| combinations(requested, &available) > 0)
+        .count()
+}
+
+fn part2(input: &str) -> usize {
+    let (available, requested) = parse(input);
+    requested
+        .map(|requested| combinations(requested, &available))
+        .sum()
+}
+
+#[cached(
+    type = "UnboundCache<(String, usize), usize>",
+    create = "{ UnboundCache::new() }",
+    convert = r#"{ (requested.to_string(), available.len()) }"#
+)]
+fn combinations(requested: &str, available: &[&str]) -> usize {
+    if requested.is_empty() {
+        return 1;
+    }
+
+    available
+        .iter()
+        .flat_map(|available| requested.strip_prefix(available))
+        .map(|requested| combinations(requested, available))
+        .sum()
+}
+
+fn parse(input: &str) -> (Vec<&str>, impl Iterator<Item = &str> + use<'_>) {
+    let (available, requested) = input.split_once("\n\n").unwrap();
+    let available = available.split(", ").collect();
+    let requested = requested.lines();
+    (available, requested)
+}