advent-of-code/2020/d05/ex2/ex2.py

42 lines
847 B
Python
Executable file

#!/usr/bin/env python
import sys
from typing import List
def seat_id(boarding_pass: str) -> int:
min_x = 0
max_x = 128
min_y = 0
max_y = 8
for char in boarding_pass:
if char == "F":
max_x = (min_x + max_x) // 2
elif char == "B":
min_x = (min_x + max_x) // 2
elif char == "L":
max_y = (min_y + max_y) // 2
elif char == "R":
min_y = (min_y + max_y) // 2
return min_x * 8 + min_y
def solve(passes: List[str]) -> int:
ids = sorted(seat_id(p) for p in passes)
for prev, cur in zip(ids, ids[1:]):
if prev + 1 != cur:
return prev + 1
assert False # Sanity check
def main() -> None:
input = [line.strip() for line in sys.stdin.readlines()]
print(solve(input))
if __name__ == "__main__":
main()