Day 19

day19.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+from functools import cache
+from typing import Optional
+
+with open('day19') as f:
+    towels = set(f.readline().strip().split(", "))
+    f.readline()
+    designs = [d.strip() for d in f]
+
+# part 1
+
+@cache
+def is_possible(design) -> Optional[list[str]]:
+    if len(design) == 0:
+        return []
+
+    collector = ""
+    for i,c in enumerate(design):
+        collector += c
+        if collector in towels:
+            rest = is_possible(design[i+1:])
+            if rest is not None: return [collector] + rest
+
+    return None
+
+
+
+cnt = 0
+for design in designs:
+   if is_possible(design):
+       cnt += 1
+
+
+# part 2
+
+@cache
+def count_possible(design) -> int:
+    if len(design) == 0:
+        return 1
+
+    collector = ""
+    count = 0
+    for i,c in enumerate(design):
+        collector += c
+        if collector in towels:
+            rest = count_possible(design[i+1:])
+            count += rest
+
+    return count
+
+
+
+cnt = 0
+for design in designs:
+    cnt += count_possible(design)