Binary Tree DFS Traversal - Inorder / Preorder / Postorder

dfsBTree.py

"""
Traversing 
"""

class Node:
    def __init__(self, key):
        self.left = None
        self.right = None
        self.value = key


def inOrder(root, visited=[]):

    if root is not None:
        inOrder(root.left, visited)
        visited.append(root.value)
        inOrder(root.right, visited)

    return visited


def postOrder(root, visited=[]):

    if root is not None:
        postOrder(root.left, visited)
        postOrder(root.right, visited)
        visited.append(root.value)

    return visited


def preOrder(root, visited=[]):

    if root is not None:
        visited.append(root.value)
        preOrder(root.left, visited)
        preOrder(root.right, visited)

    return visited


"""
Binary Tree Example:
          1
       /     \
      2       3
    /   \   /   \
   4     5 6     7
 /   \
8     9
"""

root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
root.right.left = Node(6)
root.right.right = Node(7)
root.left.left.left = Node(8)
root.left.left.right = Node(9)

traversalExamples = {
    "inOrder": inOrder(root),
    "postOrder": postOrder(root),
    "preOrder": preOrder(root),
}

for example in traversalExamples:
    print(f"{example}: {traversalExamples[example]}")