Add day 12 solutions

1 files changed, 41 insertions, 0 deletions

diff --git a/2021/12/puzzles.py b/2021/12/puzzles.py
new file mode 100644
index 0000000..8cfc506
--- /dev/null
+++ b/2021/12/puzzles.py
@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+
+from collections import defaultdict
+
+
+def solve(paths: defaultdict[list[str]], path: str) -> int:
+	acc = 0
+	tokens = path[0].split(",")
+
+	for dest in paths[tokens[-1]]:
+		if dest == "end":
+			acc += 1
+		# START PART 1
+		elif not (dest.islower() and dest in tokens):
+			acc += solve(paths, (f"{path[0]},{dest}", False))
+		# END PART 1 START PART 2
+		elif dest != "start":
+			if dest.islower() and dest in tokens:
+				if path[1]:
+					continue
+				acc += solve(paths, (f"{path[0]},{dest}", True))
+			else:
+				acc += solve(paths, (f"{path[0]},{dest}", path[1]))
+		# END PART 2
+
+	return acc
+
+
+def main() -> None:
+	paths: defaultdict[list[str]] = defaultdict(list)
+	with open("input", "r", encoding="utf-8") as f:
+		for entry in f.readlines():
+			x, y = entry.strip().split("-")
+			paths[x].append(y)
+			paths[y].append(x)
+
+	print(solve(paths, ("start", False)))
+
+
+if __name__ == "__main__":
+	main()