0069-sqrtx.c

int mySqrt(int x){
    int l = 0;
    int r = x;

    while(l <= r){
        long int m = (l + r) / 2;
        if(m * m == x){
            return m;
        }
        else if(m * m > x){
            r = m - 1;
        }
        else{
            l = m + 1;
        }
    }
    return r;
}