【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;
}