LeetCode - Sqrt(x)

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