141. x的平方根二分法

sqrt(3) = 1
sqrt(4) = 2
sqrt(5) = 2
sqrt(10) = 3

 int sqrt(int x) {
        
        int beg=0;
        int end=x;
        int mid;
        while(beg<=end)
        {
            mid=beg+(end-beg)/2;
            if(pow(mid,2)==x||(pow(mid,2)<x&&pow(mid+1,2)>x))
            {
                return mid;
            }
            else if(pow(mid,2)<x)
                beg=mid+1;
            else
                end=mid-1;
        }
        
        // write your code here
    }