2024: Day 19

Author: MiLk

2024/python/day19/__init__.py

@@ -0,0 +1,47 @@
+from collections.abc import Iterable
+from functools import cache
+from itertools import groupby
+
+from utils.file import read_input
+
+lines = read_input(__package__)
+patterns = {pattern.strip() for pattern in lines[0].split(",")}
+patterns_first_letter = {key: set(group) for key, group in groupby(sorted(patterns), lambda x: x[0])}
+max_lengths = {key: max(len(pattern) for pattern in patterns) for key, patterns in patterns_first_letter.items()}
+designs = lines[1:]
+
+
+@cache
+def is_possible(design: str) -> bool:
+    if not design:
+        return True
+    for i in range(len(design)):
+        if design[: i + 1] not in patterns_first_letter.get(design[0], []):
+            continue
+        if is_possible(design[i + 1 :]):
+            return True
+    return False
+
+
+possible_designs = [design for design in designs if is_possible(design)]
+
+# print("Part 1:", len(possible_designs))
+
+
+@cache
+def combinations(design: str) -> int:
+    end = max_lengths.get(design[0], 0)
+    if not end:
+        return 0
+
+    result = 0
+    for i in range(end):
+        if design[: i + 1] not in patterns_first_letter.get(design[0], []):
+            continue
+        if i + 1 == len(design):
+            return result + 1
+        result += combinations(design[i + 1 :])
+    return result
+
+
+print("Part 2:", sum(combinations(d) for d in possible_designs))