Top 12 Most Common Coding Interview Questions

common coding interview questions

Programming interviews can be challenging. To face the challenge and do well, you want to know the common programming interview questions to expect and what you should prepare. 

Before getting into the most common coding interview questions, you can enhance your skills in the different programming languages you are familiar with and master new languages. 

WildLearner will be your free tutor. Sign up with your Facebook, Google, or Apple accounts, and enjoy the variety of free courses. In addition to gaining new skills, you can also practice your current coding skills on WildLearner’s coding playground. 

The Most Common Programming Interview Questions

Now that you have mastered different programming languages or are on your way to doing so, let’s investigate the most common coding interview questions to prepare and present yourself diligently in the interview. 

We have divided the interview questions into several categories to make your learning process more organized and efficient. Hence, we will discuss Array, binary tree, and LinkedList questions. 

Array Programming Questions

  1. What is the default value of Array in Java?

The values Java assigns to Array by default are 0.0 for double and float and null for string.

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2. How to find the largest and the smallest numbers in an array of 1-100?

The coding approach you have to demonstrate to solve this problem is the following:


3. How to find the missing number in a given array of 1 to 100?

The following formula solves this problem: n(n+1)/2. This formula displays the sum of the first n natural numbers. The coding algorithm in Python to demonstrate the usage of this formula to find the missing number in a given array of 1 to 100 is shown below:


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4. What is an integer array?

An integer array is a combination of integers (also known as whole numbers) that programmers use for different coding purposes. 

5. How do you remove an element from an array?

Since all the elements in the array are fixed, it is not possible to edit the array and remove a particular element from it. Nonetheless, you can still do it by creating a new array and copying the material of your existing array into it, not including the element you initially wanted to remove. As a result, you will have a new array that does not contain the element you wanted to remove. 

Binary Tree Programming Questions

In programming, a binary tree is a data structure with two children nodes that contribute to its final shape. The final shape of a binary tree includes a left subtree, a right subtree, and a root node. 


Here are some of the most common coding interview questions regarding the binary tree data structure. 

  1. What are the meanings of a leaf node and a root node?

A leaf node is any node on a binary tree that does not have children. A root node is the very first node of a binary tree. 

  1. How to find the distance between two nodes in a binary tree?

When measuring the distance between two nodes, you want to consider the shortest possible answer. Thus, you simply calculate the number of edges that you have to traverse to reach from one node to the other. 

  1. How to find the lowest common ancestor (LCA) of two nodes in a binary tree?

The lowest common ancestor of two nodes in a binary tree is the node with both of the two nodes as descendants. You can find the LCA through the following steps:

  • Find paths from the root to each node separately, and store these paths in an array. 
  • Keep traversing the two paths until both arrays display the same value. 
  1. What is a binary search tree (BST)?

A binary search tree is a data structure where the value of the left node is smaller than the parent node while the value of the right node is greater than the parent node. 

  1. How to convert a binary tree into a binary search tree?

To convert a binary tree into a binary search tree, follow this algorithm of steps:

  • Create a new temporary array in which you will store the inorder traversal of your binary tree.
  • Next, sort the new temporary array you have created. 
  • Lastly, perform another inorder traversal on the tree and copy all the tree elements individually to the new tree. 

LinkedList Programming Questions

  1. What is the difference between a LinkedList and an Array data structure?

An Array contains elements that share structural similarities. Hence, they are put together under a common variable.  On the other hand, LinkedList is comprised of elements that are interconnected. Thus, in the case of LinkedList, the elements’ operational functions are related to each other.  

  1. How to remove a loop from a linked list?

AfterAcademy suggests multiple ways to approach this problem. One widely used method is hashing. Here is the coding solution offered by AfterAcademy:


Final Thoughts

To sum up, preparing properly for your coding interview is crucial for achieving success as a result. Apart from taking a look at the most common programming interview questions, you should also ensure you are skillful enough in the programming language that you have mastered. If you are still unsure about this, WildLearner has got your back by offering free programming courses for you to learn and grow.