What Is Tree in Data Structure Interview Questions?


Angela Bailey

In the field of computer science and programming, data structures are crucial for organizing and storing data efficiently. One commonly used data structure is a tree. In this article, we will explore the concept of trees in data structures and discuss some common interview questions related to trees.

What is a Tree?

A tree is a hierarchical data structure that consists of nodes connected by edges. It is similar to a real-life tree where each node represents an element, and the edges represent the relationships between these elements.

Key Terminology

Before diving into interview questions about trees, let’s familiarize ourselves with some key terminology:

  • Node: A fundamental building block of a tree that contains a value and references to its child nodes.
  • Root: The topmost node in a tree that does not have any parent nodes.
  • Parent: A node that has one or more child nodes.
  • Child: Nodes directly connected to a parent node.
  • Leaf: Nodes at the bottommost level of a tree that do not have any child nodes. They are also referred to as external nodes.
  • Internal Node: Nodes other than the root and leaf nodes are called internal nodes as they have both parent and child nodes.

Interview Questions about Trees

In technical interviews, you may come across various questions related to trees. Let’s explore some common ones:

1. What are the different types of trees?

Trees can be classified into several types based on their properties:

  • Binary Tree: A tree in which each node can have at most two children.
  • Binary Search Tree (BST): A binary tree where the left child of a node contains a value less than the parent, and the right child contains a value greater than the parent.
  • Balanced Tree: A tree in which the heights of the left and right subtrees of any node differ by at most one.
  • Complete Binary Tree: A binary tree in which all levels, except possibly the last one, are completely filled, and all nodes are as left as possible.

2. How can you traverse a tree?

There are several ways to traverse a tree:

  • Inorder Traversal: Visit the left subtree, then visit the root node, and finally visit the right subtree.
  • Preorder Traversal: Visit the root node, then visit the left subtree, and finally visit the right subtree.
  • Postorder Traversal: Visit the left subtree, then visit the right subtree, and finally visit the root node.

3. How can you determine if a binary tree is balanced?

A binary tree is considered balanced if the heights of its left and right subtrees differ by at most one. One common approach to check if a binary tree is balanced is by calculating its height recursively for each subtree and comparing them.

4. What is an AVL Tree?

An AVL (Adelson-Velsky Landis) tree is a self-balancing binary search tree in which the heights of the left and right subtrees differ by at most one. It ensures that the tree remains balanced even after insertions or deletions, by performing rotations if necessary.


Trees are fundamental data structures that play a vital role in various algorithms and applications. Understanding the concept of trees and being able to answer interview questions related to them is essential for any programmer or software engineer. With this article, you now have a solid foundation to tackle tree-related interview questions with confidence!

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