LeetCode 69. Sqrt(x)

题目

class Solution {
public:
    int mySqrt(int x) {

        long long int y=x;
        int l=0;
        int r=(x==1?1:x/2);
        while(l<=r)
        {
            long long int mid=(l+r)/2;
            if(mid*mid<y)
            {
                l=mid+1;
            }
            else if(mid*mid >y)
            {
                r=mid-1;
            }
            else
            {
                return mid;
            }
        }
        
        return r;
        
    }
};