/*
 * Return the indices that put the elements of array in sorted order
 *
 * @param array: The array to consider
 */
Integer[] argSort(color[] array) {
  IndexComparator ic = new IndexComparator(array);
  Integer[] indices = ic.createIndexArray();
  Arrays.sort(indices, ic);
  return indices;
}


/*
 A Comparator class to implement argsort
 */
class IndexComparator implements Comparator<Integer> {
  private final color[] array;

  public IndexComparator(color[] array) {
    this.array = array;
  }

  public Integer[] createIndexArray() {
    Integer [] indices = new Integer[this.array.length];
    for (int i = 0; i < array.length; i++) {
      indices[i] = i;
    }
    return indices;
  }

  public int compare(Integer index1, Integer index2) {
    return (int) (brightness(this.array[index1]) - brightness(this.array[index2]));
  }
}