DFS Binary Tree Traversal – Inorder, Postorder, and Preorder

dfs_btree_traverse.py

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),
}

import json
print(json.dumps(traversalExamples, indent=2))