infected_combination.py

from typing import List

MODULO_BASE = 10**9 + 7


def _num_combinations(m: int):
    if m <= 0:
        return 0
    half = m // 2
    return 2**half


def infected_combination(n: int, infectedHouses: List[int]) -> int:
    if len(infectedHouses) == 0:
        return 0
    total = 0
    if infectedHouses[0] > 1:
        total += 1
    if infectedHouses[-1] < n:
        total += 1
    for a, b in zip(infectedHouses, infectedHouses[1:]):
        total += _num_combinations(b - a - 1)
    return total % MODULO_BASE


print(infected_combination(12, [2, 10]))