Leetcode134: Sqrt(x)

int sqrt(int x)

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