### findRadius 
from typing import *
def f_gold(houses: List[int], heaters: List[int]) -> int:
    houses.sort()
    heaters.sort()
    def check(r):
        m, n = len(houses), len(heaters)
        i = j = 0
        while i < m:
            if j >= n:
                return False
            mi = heaters[j] - r
            mx = heaters[j] + r
            if houses[i] < mi:
                return False
            if houses[i] > mx:
                j += 1
            else:
                i += 1
        return True
    left, right = 0, int(1e9)
    while left < right:
        mid = (left + right) >> 1
        if check(mid):
            right = mid
        else:
            left = mid + 1
    return left