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HomeBusinessBinary Tree Interview Questions and Practice Problems

Binary Tree Interview Questions and Practice Problems

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Programming centers basically on data structures!

The data structures are usually of many types, such as trees, stacks, and queues. Binary trees are one of the most commonly seen ones. 

So if you aspire to become a Java developer, you will have to face interviews at some point in your life. 

To get a hold of such situations better, it is recommended to look through the most commonly asked tree interview questions.

Here we will discuss a list of all the tree interview questions that are mostly expected to be asked by an interviewer. 

Though, before that you should know in detail about binary trees. 

What is a binary tree?

To find a specific element more quickly and effectively, a binary search tree is helpful. Binary search trees mostly aid in identification when used as a prefix or postfix in expressions. With the use of binary trees, expression conversion is also possible. 

The graph traversals enable each element in the data structure to be attended to and the tasks to be completed. Binary trees can help in building a far more usable virtual memory of the object in a real-world scenario when the task at hand needs a 3D representation for better understanding.

A data structure can produce more accurate representations of data by adding binary search trees, or BST. Trees can be altered and interpreted in any way that seems appropriate since they are a sophisticated style of data display. 

When using a BST, using databases that have an index is made simpler.

Common binary tree interview questions

  1. What are leaf and root nodes?

Ans. Sometimes, interviewers ask questions about the basics of the structure. This is to get some insights into the knowledge possessed by the individual. Assessing such details helps interviewers understand if the person is a good fit for the role or not. 

Understanding nodes is one of the primary requirements and is taught during the basics class. Developers who start learning binary trees learn that a leaf node is a node without any children. They differentiate it from the root node as the top node of a tree. 

These tree interview questions help to assess not just how smart a person is but also how much they are aware of the basic details in data structure and programming. 

2. How do you check if a given binary tree is a sub-tree of another binary tree?

Ans. Finding a subset can be considered a preliminary skill learned in the initial years of studies. To see if two trees are related, you will have to find common nodes in them. If two trees have common nodes, then they will be related. 

So, a person who can find tree subsets will be aware of what nodes are and how to find them. Even though the question is basic, the whole point is to see how well the candidate knows their basic facts. 

3. What is a self-balanced tree?

Ans. A binary tree is said to be self-balanced when they have the ability to remain small when insertion or deletion operations are carried out. A binary search tree has its left subtree with lower-valued keys and right subset with high-valued ones. This is the rule that the tree follows, without exceptions. Left and right rotation is used for this. 

4. How do you convert a binary tree into a binary search tree in Java?

Ans. Tree conversions are one of the repeatedly asked amazon coding interview questions. To differentiate between a binary tree and a binary search tree, the sub-tree values are noted. A tree with left sub-tree keys of lower values and a right sub-tree of higher values is a BST. Traversal techniques are employed for this. 

For a person to understand conversions, they will need a complete knowledge of the different steps involved in it, such as:

  • Creation of temporary arrays
  • Sorting of the arrays using an algorithm
  • In-order traversal application 
  • Identification of array elements

All these steps involve a lot of techniques and applications of the algorithm. A candidate who can successfully perform the conversion of binary trees with the required tools would be adept at using an algorithm. If you are unsure of how to get better at problem-solving, practicing tree interview questions is a good start. 

Practice questions for a binary tree

Do you know why practice questions are important? 

Practicing binary tree questions should be done after mastering the theory part of the subject.

 Preparing interview questions might seem like a dead end. In reality, practicing coding questions related to interviews like amazon coding interview questions would be beneficial to solve them quickly. 

Some of the practice questions available online are related to nodes and conversions and are based on symmetry.

For example, 

  • Check if two binary trees are identical or not
  • Check if a binary tree is a sum tree or not
  • Find the diameter of a binary tree
  • Convert a binary tree to its mirror
  • Find the Lowest Common Ancestor (LCA) of two nodes in a binary tree

These questions are categorized as easy to medium. While practicing, it is also important to look out for tough questions so that you can solve any problem put in front of you with ease. 

Examples of questions with higher difficulty levels are:

– Substituting the provided numbers with the corresponding alphabets will create word combinations

– Calculate the separation between specific pairs of nodes in a binary tree.

– Sink nodes with zero are at the base of a binary tree.

– Create a complete binary tree from the pre-order sequence with knowledge of the leaf nodes.

Are you wondering if practicing these questions is enough? The more you practice, the more pro you will become!

These practice questions cover almost all topics that come under binary trees and help in grasping the concept quicker. 


 Working on binary tree interview questions can be an excellent idea since it will familiarize a person with the questions they may face in an interview. Having an idea beforehand gives them an edge to ace the interview. 

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