2024 day 19.

src/holt59/aoc/2024/day19.py

@@ -1,7 +1,42 @@
+from functools import cache
 from typing import Any, Iterator
 
 from ..base import BaseSolver
 
 
+@cache
+def is_valid(design: str, towels: tuple[str, ...]) -> bool:
+    if not design:
+        return True
+
+    return any(
+        design.startswith(towel) and is_valid(design[len(towel) :], towels)
+        for towel in towels
+    )
+
+
+@cache
+def count_valid(design: str, towels: tuple[str, ...]) -> int:
+    if not design:
+        return 1
+
+    return sum(
+        design.startswith(towel) and count_valid(design[len(towel) :], towels)
+        for towel in towels
+    )
+
+
 class Solver(BaseSolver):
-    def solve(self, input: str) -> Iterator[Any]: ...
+    def solve(self, input: str) -> Iterator[Any]:
+        towels_s, designs_s = input.split("\n\n")
+
+        towels = tuple(s.strip() for s in towels_s.split(","))
+
+        designs = [
+            design
+            for design in self.progress.wrap(designs_s.splitlines())
+            if is_valid(design, towels)
+        ]
+
+        yield len(designs)
+        yield sum(count_valid(design, towels) for design in self.progress.wrap(designs))