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#!/usr/bin/env python3
from collections import defaultdict
def solve(paths: defaultdict[str, list[str]], path: str, flag: bool = False) -> int:
acc = 0
tokens = path.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},{dest}")
# END PART 1 START PART 2
elif dest != "start":
if dest.islower() and dest in tokens:
if flag:
continue
acc += solve(paths, f"{path},{dest}", True)
else:
acc += solve(paths, f"{path},{dest}", flag)
# END PART 2
return acc
def main() -> None:
paths: defaultdict[str, 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()
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