【Leetcode】Sqrt(x)

题目链接：https://leetcode.com/problems/sqrtx/
题目：

Implement int sqrt(int x).

Compute and return the square root of x.

思路：

 二分法搜索平方数 要注意，如果不能完整的开方，要取靠左边的数，

算法：

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