69. Sqrt(x)

binary search method 
class Solution(object):
    def mySqrt(self, x):
        """
        :type x: int
        :rtype: int
        """
        if x<=1: return x
        left,right=1,x/2
        while True: 
            mid=(left+right)/2 
            if mid*mid>x:
                right=mid-1
            else: 
                if (mid+1)*(mid+1)>x:return mid
                left=mid+1 

newton integer method 
class Solution(object):
    def mySqrt(self, x):
        """
        :type x: int
        :rtype: int
        """
        a=x
        while a*a>x:
            a=(a+x/a)/2
        return a