/**
 * @param h - height of tree
 * @param bf - branching factor
 * @param rand - random generator for generating elements
 */
static Tree<Integer> generateTree(int h, int bf, Random rand) {
  Tree<Integer> t = new Tree<Integer>(rand.nextInt(10));

  for (int i = 0; i < bf & h > 0; i++) {
    t.addSubtree(generateTree(h-1, bf, rand));
  }

  return t;
}