Leetcode 69 X的平方根C++

思路：二分法。

class Solution {
public:
    int mySqrt(int x) {
        if(x<=1) return x;
        int left =0,right=x;
        while(left<right)
        {
            int mid=(left+right)/2;
            if(x/mid>=mid) left=mid+1;
            else right=mid;
        }
      return right-1;
    }
};