2024 day 25.

src/holt59/aoc/2024/day25.py

@@ -1,7 +1,40 @@
+import itertools as it
 from typing import Any, Iterator
 
 from ..base import BaseSolver
 
 
+def read_locks_and_keys(input: str):
+    locks: list[tuple[int, ...]] = []
+    keys: list[tuple[int, ...]] = []
+
+    for block in map(str.splitlines, input.split("\n\n")):
+        n_rows, n_cols = len(block), len(block[0])
+        if block[0] == "#" * n_cols:
+            locks.append(
+                tuple(
+                    next(i for i in range(n_rows) if block[i][j] == ".") - 1
+                    for j in range(n_cols)
+                )
+            )
+        else:
+            keys.append(
+                tuple(
+                    n_rows - next(i for i in range(n_rows) if block[i][j] == "#") - 1
+                    for j in range(n_cols)
+                )
+            )
+
+    return locks, keys
+
+
 class Solver(BaseSolver):
-    def solve(self, input: str) -> Iterator[Any]: ...
+    def solve(self, input: str) -> Iterator[Any]:
+        locks, keys = read_locks_and_keys(input)
+        assert len(set(locks)) == len(locks)
+        assert len(set(keys)) == len(keys)
+
+        yield sum(
+            all(c1 + c2 <= 5 for c1, c2 in zip(lock, key, strict=True))
+            for lock, key in it.product(locks, keys)
+        )

src/holt59/aoc/inputs/tests/2024/day25.txt

@@ -0,0 +1,39 @@
+#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####