Vertical Order Traversal of Binary Tree in DSA Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Vertical Order Traversal of a Binary Tree?

It is a way to print the nodes of a binary tree column by column, from left to right. Nodes in the same vertical line are grouped together.

beginner

How do we assign vertical levels to nodes in Vertical Order Traversal?

The root node is at vertical level 0. Left child nodes decrease the vertical level by 1, right child nodes increase it by 1.

intermediate

Which data structure is commonly used to store nodes by their vertical levels during traversal?

A map or dictionary with keys as vertical levels and values as lists of nodes at that level.

intermediate

Why do we use a queue in Vertical Order Traversal?

A queue helps us do a level order traversal (breadth-first) so nodes are processed top to bottom within each vertical line.

advanced

What is the output order when multiple nodes share the same vertical and horizontal level?

They are printed in the order they appear in the level order traversal (top to bottom, left to right).

In Vertical Order Traversal, what vertical level is assigned to the root node?

A 1

B 0

C -1

D Depends on tree height

The root node is always assigned vertical level 0.

Which data structure is best to keep track of nodes and their vertical levels during traversal?

A Stack

B Queue

C Set

D Map/Dictionary

A map/dictionary stores vertical levels as keys and lists of nodes as values.

When traversing the tree, how do you update the vertical level for the right child?

A vertical level

B vertical level - 1

C vertical level + 1

D vertical level * 2

Right child nodes increase the vertical level by 1.

What traversal method is commonly combined with vertical level tracking for this problem?

A Level order (BFS)

B Inorder

C Postorder

D Preorder

Level order traversal ensures nodes are processed top to bottom.

If two nodes share the same vertical and horizontal level, how is their order decided in output?

A Order of insertion in traversal

B Value size order

C Random order

D Alphabetical order

They appear in the order they are visited during level order traversal.

Explain how vertical levels are assigned and used in Vertical Order Traversal of a binary tree.

Think about how you move left or right from the root.

Describe the role of a queue and a map/dictionary in implementing Vertical Order Traversal.

One helps visit nodes in order, the other helps group them.