func findRadius(houses []int, heaters []int) (radius int) {
	sort.Ints(heaters)
	n := len(heaters)
	for _, i := range houses {
		beg, end := 0, n-1
		for beg <= end {
			mid := beg + (end-beg)/2
			if heaters[mid] < i {
				beg = mid + 1
			} else {
				end = mid - 1
			}
		}
		if beg == 0 {
			radius = maxInt(radius, heaters[beg]-i)
		} else if beg == n {
			radius = maxInt(radius, i-heaters[n-1])
		} else {
			radius = maxInt(radius, minInt(i-heaters[beg-1], heaters[beg]-i))
		}
	}
	return
}

func minInt(x, y int) int {
	if x < y {
		return x
	}
	return y
}

func maxInt(x, y int) int {
	if x < y {
		return y
	}
	return x
}