advent-of-code/2021/d12/ex1/ex1.py

47 lines
901 B
Python
Executable file

#!/usr/bin/env python
import itertools
import sys
from collections import defaultdict
from typing import Dict, List, Set
Map = Dict[str, Set[str]]
def solve(input: List[str]) -> int:
def parse() -> Map:
res: Map = defaultdict(set)
for (start, to) in map(lambda s: s.split("-"), input):
res[start].add(to)
res[to].add(start)
return res
caves = parse()
def dfs(start: str, seen: Set[str] = set()) -> int:
if start == "end":
return 1
seen = seen | {start}
res = 0
for dest in caves[start]:
if dest in seen and dest.islower():
continue
res += dfs(dest, seen)
return res
return dfs("start")
def main() -> None:
input = [line.strip() for line in sys.stdin.readlines()]
print(solve(input))
if __name__ == "__main__":
main()