advent-of-code/2020/d19/ex2/ex2.py

58 lines
1.6 KiB
Python
Executable file

#!/usr/bin/env python
import itertools
import re
import sys
from typing import Dict, List
def parse_rule(raw_rules: List[str]) -> str:
parsed: Dict[int, str] = {}
rules = {int(num): rule.strip() for num, rule in (i.split(":") for i in raw_rules)}
for n, r in rules.items():
if '"' not in r:
continue
parsed[n] = r.replace('"', "")
while 0 not in parsed:
for num in parsed:
if num not in rules:
continue
rules.pop(num)
for num, r in rules.items():
nums = list(reversed(sorted(map(int, re.findall("(\\d+)", r)))))
if all(n in parsed for n in nums):
for n in nums:
r = re.sub(str(n), parsed[n], r) # Bigger numbers replaced first
r = r.replace(" ", "{x}" if num == 11 else "")
if num == 11:
r = "(" + r + "{x})"
r = "(" + r + ")"
if num == 8:
r = "(" + r + "+)"
parsed[num] = r
return parsed[0]
def solve(raw: List[str]) -> int:
pattern = parse_rule(list(itertools.takewhile(len, raw)))
def matches(repeats: int) -> int:
pat = re.compile(pattern.replace("x", str(repeats)))
return sum(
pat.fullmatch(line) is not None for line in itertools.dropwhile(len, raw)
)
return sum(itertools.takewhile(bool, map(matches, itertools.count(1))))
def main() -> None:
input = [line.strip() for line in sys.stdin.readlines()]
print(solve(input))
if __name__ == "__main__":
main()