/* Initializes |larger| and |smaller| within range |min|@dots{}|max| of
   |array[]|,
   which has |n| real elements plus a |(n + 1)|th sentinel element. */
int
init_binary_tree_array (struct binary_tree_entry array[], int n,
                        int min, int max)
{
  if (min <= max)
    {
      /* The `|+ 1|' is necessary because the tree root must be at |n / 2|,
         and on the first call we have |min == 0| and |max == n - 1|. */
      int i = (min + max + 1) / 2;
      array[i].larger = init_binary_tree_array (array, n, i + 1, max);
      array[i].smaller = init_binary_tree_array (array, n, min, i - 1);
      return i;
    }
  else
    return n;
}