Sqrt(x)

 https://leetcode.com/problems/sqrtx/

 Simplest Approach:

class Solution {
public:

    int mySqrt(int x) {
        long long int y=0;
        while(y*y<=x)
        {
            y++;
        }
        return y-1;
    }
}; 

optimal using binary search:

class Solution {
public:

    int mySqrt(int x) {
       long long int s=0,e=INT_MAX,ans=0;
        while(s<=e)
        {
            long long int m=s+(e-s)/2;
            if(m*m <=x)
            {
                ans=m;
                s=m+1;
            }
            else{
                e=m-1;
            }
        }
        return ans;
    }
};