int *heap = new int[size];
  heap[0] = index[0];
  for(int i = 1; i < size; i++)
  {
    heap[i] = index[i];
    // Compare to the parent
    for (int j = i; j > 0; j >>= 1)
      if (customers[heap[(j - 1) >> 1]] < customers[heap[j]])
      { // Swap
        /*
        heap[j] ^= heap[(j - 1) >> 1];
        heap[(j - 1) >> 1] ^= heap[j];
        heap[j] ^= heap[(j - 1) >> 1];
        */
        int temp = heap[(j - 1) >> 1];
        heap[(j - 1) >> 1] = heap[j];
        heap[j] = temp;
      }
      else
        break;
  }