private static void sort(int[] arr)
    {
        int zero = 0, back = arr.length - 1;
        
        for (int i : arr)
        {
            if (i == 0)
                zero++;
        }
        
        for (int i = 0; i < arr.length; i++)
        {
            if (arr[i] == 1 && i < zero)
            {
                arr[i] = arr[back];
                arr[back] = 1;
                back--;
                i--;
            }
        }
    }