DSA · Theory

Postorder Traversal

Theory

145/810

Postorder Traversal

Postorder Traversal is a DSA topic. In plain words you use it for a short Postorder Traversal example in a short dry-run on paper. Don’t start with a slogan — start with that picture.

Smallest example: the smallest Postorder Traversal example you can type. Type it, run it, and say what you see. If you can do that from memory, you know Postorder Traversal.

From the example next to this theory — Postorder Traversal — inorder walks left → node → right (sorted order for a BST).

Trap — only saying “Postorder Traversal” with no example. Fix that before you talk about advanced DSA.

Viva — what is Postorder Traversal? Then show the smallest Postorder Traversal example you can type. Then name the trap.

Exam tip

What is Postorder Traversal? Show this: the smallest Postorder Traversal example you can type. Trap: only saying “Postorder Traversal” with no example.

Example

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

def inorder(n):
    if not n:
        return []
    return inorder(n.left) + [n.val] + inorder(n.right)

root = Node(2, Node(1), Node(3))
print(inorder(root))

Postorder Traversal — inorder walks left → node → right (sorted order for a BST).

Short notes

DefPostorder Traversal — a short Postorder Traversal example in a short dry-run on paper.
Rulethe smallest Postorder Traversal example you can type
Traponly saying “Postorder Traversal” with no example
Usea short dry-run on paper

DSA · Theory

Postorder Traversal

← All stacks

Theory

145/810

Postorder Traversal

Postorder Traversal is a DSA topic. In plain words you use it for a short Postorder Traversal example in a short dry-run on paper. Don’t start with a slogan — start with that picture.

Smallest example: the smallest Postorder Traversal example you can type. Type it, run it, and say what you see. If you can do that from memory, you know Postorder Traversal.

From the example next to this theory — Postorder Traversal — inorder walks left → node → right (sorted order for a BST).

Trap — only saying “Postorder Traversal” with no example. Fix that before you talk about advanced DSA.

Viva — what is Postorder Traversal? Then show the smallest Postorder Traversal example you can type. Then name the trap.

Exam tip

What is Postorder Traversal? Show this: the smallest Postorder Traversal example you can type. Trap: only saying “Postorder Traversal” with no example.

Example

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

def inorder(n):
    if not n:
        return []
    return inorder(n.left) + [n.val] + inorder(n.right)

root = Node(2, Node(1), Node(3))
print(inorder(root))

Postorder Traversal — inorder walks left → node → right (sorted order for a BST).

Short notes

DefPostorder Traversal — a short Postorder Traversal example in a short dry-run on paper.
Rulethe smallest Postorder Traversal example you can type
Traponly saying “Postorder Traversal” with no example
Usea short dry-run on paper

Postorder Traversal

Example

Short notes

Questions

Postorder Traversal

Example

Short notes

Questions