leetcode69 Sqrt(x)

Implement int sqrt(int x).

Compute and return the square root of x.

class Solution {//二分
public:
    int mySqrt(int x) {
        if(x<=1)
            return x;
        int a=1,b=x;
        int m;
        while(a<=b)
        {
            m=a+(b-a)/2; //防止溢出
            int y=x/m;
            if(m==y)   //防止溢出
            {
                return m;
            }
            if(m<y)
            {
                a=m+1;
            }
            else
                b=m-1;
        }
        return b;
    }
};