def main():
tree = BST()
N = 10
_set = set([random.randint(1, N * N) for _ in range(N)])
for x in _set:
tree.insert(x, "")
tree.pretty_print()
postorder = [node.key for node in tree.postorder_nodes()]
print postorder
postorder_iterator = PostorderIterator(tree.root)
idx = 0
while postorder_iterator.has_next():
postorder_iterator.next() is postorder[idx]
idx += 1
