4.11.2 Aside: Recursive Destruction

The algorithm used in the previous section is easy and fast, but it is not the most common method for destroying a tree. The usual way is to perform a traversal of the tree, in much the same way we did for tree traversal and copying. Once again, we'll start from a recursive implementation, because these are so easy to write. The only tricky part is that subtrees have to be freed before the root. This code is hard-wired to use free() for simplicity:

86. <Destroy a BST recursively 86> =
static void 
bst_destroy_recursive (struct bst_node *node) 
{
  if (node == NULL)
    return;

  bst_destroy_recursive (node->bst_link[0]);
  bst_destroy_recursive (node->bst_link[1]);
  free (node);
}