2021-10-05

查找x的平方根，并且结果向下取整。

class Solution(object):
    def mySqrt(self, x):
        """
        :type x: int
        :rtype: int
        """
        l = 0
        r = x
        ans = - 1
        if x == 0:
            return 0
        elif x==1:
            return 1
        while l <= r:
            m = l +(r-l)/2
            if m > x/m:
                r = m-1
            elif m <= x/m:
                ans = m
                l = m+1
        return ans