advent-of-code/2020/d09/ex2/ex2.py

43 lines
993 B
Python
Executable file

#!/usr/bin/env python
import itertools
import sys
from typing import List
def find_invalid(nums: List[int]) -> int:
for i in range(25, len(nums)):
num = nums[i]
found = False
for lhs, rhs in itertools.combinations(nums[i - 25 : i], 2):
if lhs + rhs == num:
found = True
break
if not found:
return num
assert False # Sanity check
def find_weakness(nums: List[int], invalid: int) -> int:
for i in range(len(nums) - 2):
for j in range(i + 2, len(nums)):
if sum(nums[i:j]) == invalid:
return min(nums[i:j]) + max(nums[i:j])
assert False # Sanity check((
def solve(raw: List[str]) -> int:
nums = [int(line) for line in raw]
invalid = find_invalid(nums)
return find_weakness(nums, invalid)
def main() -> None:
input = [line.strip() for line in sys.stdin.readlines()]
print(solve(input))
if __name__ == "__main__":
main()