✅ Postorder Traversal in Binary Search Tree (BST)

Follow Me

In Postorder traversal, the order of visiting nodes is:

Left → Right → Root

This traversal is useful for deleting the tree, as it visits children before the parent node.

🌳 Example Binary Search Tree:

40 / \ 20 60 / \ / \ 10 30 50 70

🔁 Postorder Traversal Step-by-Step:

1. Traverse left subtree →
2. Traverse right subtree →
3. Visit root

🔢 Postorder Traversal Output:

10 → 30 → 20 → 50 → 70 → 60 → 40

📌 Python Code:

class Node: def __init__(self, key): self.left = None self.right = None self.val = key def postorder(root): if root: postorder(root.left) postorder(root.right) print(root.val, end=" ") # Create BST root = Node(40) root.left = Node(20) root.right = Node(60) root.left.left = Node(10) root.left.right = Node(30) root.right.left = Node(50) root.right.right = Node(70) # Postorder Traversal postorder(root)

📌 Key Point:

✅ Postorder traversal is best for deleting or freeing memory (bottom-up approach).