2020: d13: ex2: add solution

This commit is contained in:
Bruno BELANYI 2020-12-13 07:39:21 +01:00
parent b26314c942
commit f071afb02b

45
2020/d13/ex2/ex2.py Executable file
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#!/usr/bin/env python
import math
import sys
from typing import Dict, List
def run_contest(timings: List[int]) -> int:
# https://rosettacode.org/wiki/Chinese_remainder_theorem#Python_3.6
def mul_inv(a: int, b: int) -> int:
b0 = b
x0, x1 = 0, 1
if b == 1:
return 1
while a > 1:
q = a // b
a, b = b, a % b
x0, x1 = x1 - q * x0, x0
if x1 < 0:
x1 += b0
return x1
def chinese_remainder(residue_mapping: Dict[int, int]) -> int:
res = 0
prod = math.prod(residue_mapping)
for n_i, a_i in residue_mapping.items():
p = prod // n_i
res += a_i * mul_inv(p, n_i) * p
return res % prod
residues = {t: -i for (i, t) in enumerate(timings) if t > 0}
return chinese_remainder(residues)
def solve(raw: List[str]) -> int:
return run_contest([int(i) if i != "x" else -1 for i in raw[1].split(",")])
def main() -> None:
input = [line.strip() for line in sys.stdin.readlines()]
print(solve(input))
if __name__ == "__main__":
main()