Sqrt(x)

Implementint sqrt(int x).

Compute and return the square root of x.

注意：Submission Result:Time Limit Exceeded。因为mid * mid will overflow when mid>sqrt(INT_MAX)

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

二刷：

九章模版

注意循环结束后判断条件，例如sqrt（8）＝2

class Solution(object):
    def mySqrt(self, x):
        """
        :type x: int
        :rtype: int
        """
        start, end = 1, x
        while start+1 < end:
            mid = (start+end)/2
            if mid*mid < x:
                start = mid
            else:
                end = mid
        if end * end <= x:
            return end
        return start