Tree Data Structure Questions for Coding Interviews Preparation

Hey guys, I have shared a lot of resources about programming job interviews like books, courses and some interview questions about software design and data structures like matrix, string and linked list.

So far, we’ve only looked at Linear Data Structures, such as an array and a linked list, but not all the information in the real world can be represented in a linear way, and here the tree data structure helps.

A tree data structure is a hierarchical data structure that allows you to store hierarchical data such as a family tree or an office hierarchy. Depending on how the data is stored, there are different types of trees, such as a binary tree, where each node contains at most two child nodes.

Besides its close cousin binary search tree, it is also one of the most popular tree data structures. Therefore, you will find a lot of questions based on it, such as how to pass it, count nodes, find depth, check if it is balanced or not.

The main point of solving binary tree questions is a strong knowledge of theory, Such as what is the size or depth of a binary tree, what is a leaf, what is a node, as well as an understanding of common traversal algorithms, such as pre-order traversal, post-order, and sort.

If you are not familiar with these concepts, I highly suggest you to first go through the comprehensive data structure and algorithm course which explains the underlying data structure in detail.

Binary tree-based coding problems for interviews

Now that you know how to solve tree-based binary coding problems using recursion and some tips on solving tree-based coding problems, here is a list of common questions about binary tree-based coding from software engineer or developer job interviews:

  1. What is the difference between binary and binary search trees? (Answer)
    Binary Tree is a basic structure that has a simple rule that no parent should have more than two children while binary search tree is a variant of the binary tree that follows a certain order in which nodes must be organized. In a binary search tree, the values ​​of the nodes on the left subtree are less than or equal to the root, and the values ​​of nodes in the right subtree are greater than or equal to the root.

  2. What is a self-balancing tree? (Answer)
    Self-balancing binary search trees are height-balanced binary search trees that automatically keep the height as small as possible when insertion or deletion occurs. Hence, for self-balancing BSTs, the minimum height must be rounded down. In other words, a tree is balanced if the height of the left and right subtree differs from each node in the tree by at most 1

  3. What is an AVL tree? (Answer)
    The AVL tree is a self-balancing binary search tree. It was the first data structure to be invented. In an AVL tree, the heights of the two child subtrees of any node differ by at most one; If at any time they differ by more than one, a rebalancing is done to restore that characteristic

  4. How do you perform an internal traversal in a given binary tree? (solution)

    binary tree

  5. How do you print all nodes of a given binary tree using inside traversal without iteration?
    You can use the stack to replace the recursion as given in the solution (solution)

  6. How do you implement the postal order traversal algorithm? (solution)
    Postorder means LRN (left tree, right tree, node), which means the root is visited last

  7. How are all sheets of a binary search tree printed? (Answer)
    Here are the steps you can follow to print all the leaf nodes of a binary tree:

    1. If giving a tree node or an empty root, go back.
    2. Print the node If the left and right tree are null, then this is the leaf node.
    3. Repeat the process with both the left and right subtrees.
  8. How do you calculate the number of leaf nodes in a given binary tree? (Answer)

    Here is an iterative algorithm to get the total number of leaf nodes of a binary tree:

    1. If the root is empty, return zero.
    2. Start counting with zero.
    3. Push Root to Stack.
    4. Iterates until the stack is not empty.
    5. Pop the last node and push the left and right children of the last node if they are not empty.
  9. How is a binary search tree implemented? (solution)
    The binary tree is implemented with the help of objects. The root object represents the first node in the tree. Each node in the tree consists of three parts, i.e. data, left node and right node. To create a binary tree, we first need to create the node or TreeNode object like this:

    class TreeNode{
      TreeNode right;
      TreeNode left;
      int data;

  10. How do you traverse a given binary tree in the pre-order without iterating? (solution)
    Pre-order traversal in Java without iteration

    1. Create an empty stack.
    2. Push Root to Stack.
    3. Iterates until the stack is empty.
    4. Pop out the last node and print its value.
    5. Push the left and right knots if they are not empty.
    6. Repeat steps 4 through 6 again.
  11. What is Trie Data Structure? (Answer)
    A triangle is an ordered data structure, which is a type of search tree used to store relational data structures. It is also referred to as the root tree or the prefix tree.

  12. What is the difference between Binary Tree and Trie? (Answer)
    Unlike a binary search tree, the nodes in the triangle do not store the key associated with them. Instead, the position of the node in the triangle determines which key it is associated with. This distributes the value of each key across the data structure and means that not every node has to have an associated value.

These are some of the most common binary tree based questions asked in programming job interviews. You can solve it to become comfortable with tree based problems.

If you feel that your understanding of binary tree coding is insufficient and you cannot solve these questions on your own, I suggest you go back and choose a good data structure and algorithm course to refresh your knowledge about binary tree and binary search tree.

You are now one step closer to the coding interview

These are some of the most frequently asked questions about binary tree data structure from coding interviews that help you do well in your interview.

these Frequently Asked Questions About Coding, Data Structure and Algorithm They are the people you need to know for a successful interview with any company, big or small, for any level of programming jobs.

If you are looking for a programming or software development job in 2021, you can start preparing with this list of coding questions. This list provides good topics for preparation and also helps assess your willingness to know your areas of strength and weakness.

Good knowledge of data structure and algorithms is crucial to success in coding interviews and this is where you should focus most of your attention.


Thanks, you have reached the end of the article. Good luck on your programming interview! It certainly won’t be easy, but by following our roadmap and guide, you are one step closer to becoming a software developer.

Note – If you need some free resources, you can check out this list of free Data Structure and Algorithm courses to start preparing.


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