【leetcode刷题】T187-x 的平方根

示例 1:
输入: 4
输出: 2

示例 2:
输入: 8
输出: 2
说明: 8 的平方根是 2.82842..., 
     由于返回类型是整数，小数部分将被舍去。

while l <= r:
    if mid * mid <= x:
        l = mid + 1
    else:
        r = mid -1
# 最后结果：r*r <= x < l
return l - 1

class Solution(object):
    def mySqrt(self, x):
        """
        :type x: int
        :rtype: int
        """
        num = 0
        while num * num <= x:
            num += 1
        return num - 1

class Solution(object):
    def mySqrt(self, x):
        l, r = 0, x
        while l <= r:
            mid = (l + r) / 2
            val = mid * mid
            if val <= x:
                l = mid + 1
            else:
                r = mid - 1
        return l - 1