def postorder(tree: BinaryTree):
"""
Aka 'backward order'.
In a postorder traversal, we recursively do a postorder
traversal of the left subtree and the right subtree
followed by a visit to the root node.
"""
if tree:
postorder(tree.get_left_child())
postorder(tree.get_right_child())
print(tree.get_root_value())
def inorder(tree: BinaryTree):
"""
Aka 'symmetric order'.
In an inorder traversal, we recursively do an inorder
traversal on the left subtree, visit the root node,
and finally do a recursive inorder traversal of the
right subtree.
"""
if tree:
inorder(tree.get_left_child())
print(tree.get_root_value())
inorder(tree.get_right_child())
def preorder(tree: BinaryTree):
"""
Aka 'forward order'.
In a preorder traversal, we visit the root node first,
then recursively do a preorder traversal of the left
subtree, followed by a recursive preorder traversal
of the right subtree.
"""
if tree:
print(tree.get_root_value())
preorder(tree.get_left_child())
preorder(tree.get_right_child())
Aka 'backward order'.
In a postorder traversal, we recursively do a postorder
traversal of the left subtree and the right subtree
followed by a visit to the root node.
"""
if tree:
postorder(tree.get_left_child())
postorder(tree.get_right_child())
print(tree.get_root_value())
if __name__ == '__main__':
bt = BinaryTree('0')
bt.insert_left('1')
bt.insert_right('2')
left = bt.get_left_child()
right = bt.get_right_child()
left.insert_left('1.1')
left.insert_right('1.2')
right.insert_left('2.1')
right.insert_right('2.2')
""" Tree representation:
___0___
/ \
1 2
/ \ / \
1.1 1.2 2.1 2.2
"""
print("Preorder traversal:")
preorder(bt)