367有效的完全平方数.md

func isPerfectSquare(num int) bool {
    left, right := 0, num
    for left <= right {
        mid := left + (right - left) / 2
        if mid * mid == num {
            return true
        } else if mid * mid > num {
            right = mid - 1
        } else {
            left = mid + 1
        }
    }
    return false
}