The Top 40 Coding Interview Questions (Plus 4 Tips for Winning the Job)

Alex Bell

You’ve taken the classes…

You’ve programmed the projects…

And now it’s time to get the job you’ve been gunning for. 

The next, and perhaps final step, is nailing the interview. 

Coding interviews are notoriously stressful and agonizing, in large part because of the difficult questions you’ll be asked. 

Knowing beforehand what will be asked and having a great answer can make the difference between getting called in for your first day or trudging along to yet another interview. 

In this post, we’ll show you 50 of the top interview questions you’re likely to be asked so you’ll be well-prepared to give solid answers. 

But before we do, let’s take a look at a few tips for making the interview as smooth as possible. 

4 Tips for Crushing Your Coding Interview Questions

Animated woman answering coding interview questions
Acing your interview is as much about how you present yourself and communicate as it is about your programming knowledge


Research the company (and your interviewer)

Before sitting down for an interview, you should know as much as possible about the company and the person interviewing you. 

Look for the products and projects they’ve created and are working on. Use some of their products if possible, and be able to speak intelligently about them.

Identify the core technologies and frameworks they use in coding. 

Have a general understanding of their target market and niche domain they operate in. 

Look up the interviewer on LinkedIn. This helps you “know your audience.” An HR director probably won’t understand a lot of technical jargon, so you should prepare a different approach to the interview with them than you would with a lead software engineer. 

Researching before the interview allows you to have relevant talking points and displays your genuine interest in the company. But perhaps more importantly, it gives you a clear idea of how your current skills align with the job requirements and lets you assess how well you’ll fit in the organization. 

Be personable and confident

The first interview might be your only shot at a great first impression. Although you’re applying for a job that doesn’t require outstanding social and soft skills, being personable and confident goes a long way in making you stand out from other candidates. 

Be energetic without being frantic and enthusiastic without being obnoxious. 

Give a proper handshake and make consistent eye contact. 

Being friendly and likable also demonstrates to the interviewer that you could be a great team player. If hired, you’ll be working alongside many other software engineers, stakeholders, and members of other teams within the organization. Your communication skills will be weighed against your technical abilities when deciding who to hire. 

Pay attention to your body language

Your body language and that of the interviewer can largely dictate how you’re perceived as a candidate and how well the interview goes. 

Being sweaty or clammy in an interview can make you seem unable to handle the pressures of the coding job you’re applying for. 

Bad posture can make you look lazy, even unattractive, and can trigger unconscious biases in the interviewer’s mind.

Tapping your foot, fiddling with a pen, or nervously playing with your hair can be extremely distracting to some people and make you come off as unfocused, too hyperactive, and possibly unable to be productive and work the demanding hours of a coder. 

Those are just 3 examples of your own body language to pay attention to. 

Calming yourself as best you can, sitting with proper posture, controlling your body movements, smiling, etc. are positive nonverbal cues that silently influence the interviewer toward liking and recommending you, increasing your likelihood of being hired. 

On the other side of the table, you should pay attention to the interviewer’s body language. 

If you give a long response to a question and the interviewer clears their throat, for example, this may tell you to be more concise in your answers. 

Focus on how the interviewer reacts to your answers to understand how to keep them engaged, maintain a good conversational flow, and possibly even turn the tide of the interview if you notice it’s going south. 

Know your projects inside and out

The coding interview questions you’ll be asked are designed to judge your ability to talk about software broadly and in fine detail. 

Your resume will list the projects you’ve performed in the past and the interviewer is likely to probe into them. 

If the question is vague such as, “Can you tell me about this project?” Don’t launch into the deep technical aspects right away. Tell a “story” about its creation, starting from the front-end application and what you used to develop it, through to the user inputs that informed its design. Then work backward to the modules within the application all the way to the persistent data database.

By noting every level of development and the specific software programs used for them, you demonstrate a deep understanding of the total infrastructure of a given project and the capability to execute these same tasks for their organization.

40 Top Programming Interview Questions

Silhouettes with a question mark and lightbulb brain
Interviewers will throw out some of their best coding interview questions and you have to be prepared to answer a wide variety of them.


String Coding Interview Questions

  1. How do you find the first non-repeated character in a string?
  2. How would you convert a byte array to string?
  3. How do you count the number of occurrences in string of any given character?
  4. How would you remove duplicates from string?
  5. How would you convert string to integer and integer to string?
  6. How do you count the number of vowels or consonants in a string?
  7. How would you approach checking if two strings are actually a rotation of one another?
  8. How do you build a regular expression to determine if String is a number?
  9. How do you check if a set of strings are anagrams of one another?
  10. How do you find duplicates in a string?

Array Coding Interview Questions

  1. How do you find and remove duplicates from an integer array without using collection API classes?
  2. How do you reverse an array in Java?
  3. In an integer array of 1-100, how do you find the missing elements?
  4. How do you find the smallest and largest number in an integer array?
  5. How would you approach finding pairs of integers whose sum equals that of a given number?
  6. How do you sort an integer array using the quicksort algorithm?
  7. Can you tell me the difference between array and linked list?
  8. In any given array, how do you perform a binary search?
  9. How would you approach finding repeated numbers in an array when it contains multiple duplicates?
  10. How do you find the minimum value in a rotated sorted array?

Sorting Coding Interview Questions

  1. Can you tell me the difference between quicksort and counting sort based coding algorithms?
  2. Do you know the difference between an unstable and stable sorting algorithm?
  3. What is the difference between a stable and unstable sorting algorithm?
  4. How do you write an iterative version of the quicksort algorithm?
  5. What is the bubble sort algorithm and how do you implement it?
  6. How do you remove duplicate nodes from an unsorted linked list?
  7. What is an insertion sort algorithm and how do you implement it?
  8. How do you convert a sorted list into a binary search tree?
  9. What is a bucket sort algorithm and how is it implemented?
  10. How do you remove duplicates from a sorted linked list?

Binary Tree Coding Interview Questions

  1. How do you calculate the height of a binary tree?
  2. How do you print all nodes of a given binary tree in specific order?
  3. How do you find the diameter of a binary tree?
  4. How do you find the lowest common ancestor of two nodes in a binary tree?
  5. How do you find vertical sum in a given binary tree?
  6. How do you convert a binary tree to a full tree by removing nodes?
  7. How would you approach finding all nodes at a given distance from leaf nodes in a binary tree?
  8. How do you find the maximum difference between a node and its descendants in a binary tree?
  9. How do you find the maximum sub path between two leaves in a binary tree?
  10. How do you construct a cartesian tree from in-order traversal?

How to Communicate Better with Your New Team After You Get the Job

These coding interview questions and tips can help you do well in the interview and get hired. 

But like we mentioned in one of our tips: technical skills aren’t all you need once on the job. 

Communication skills are almost as important as your ability to code. 

But here’s the thing:

Emails, texts, calls…

None of them possess the persuasive power of showing your face or visually demonstrating what you’re talking about.

Programming is all about problem-solving. 

Visual communication helps you reduce miscommunication and mistakes when solving problems with your team. 

The documentation you present can be enhanced with annotated screenshots and screen recordings to show how to properly implement your code. 

Creating a GIF to capture a bug and sharing it in a pull request or on Slack, GitHub, Jira, or anywhere else your team communicates speeds up understanding without relying on confusing messages or calls. 

And CloudApp lets you do it all and more. 

We bring HD screen and webcam recording to the cloud in an easy-to-use, enterprise-grade app so you can quickly create and share visual content.

CloudApp is used as an essential programming productivity tool by over 3 million people and is trusted by top companies such as Uber, Salesforce, and Adobe. 

We’ve been ranked by G2 Crowd as one of the top sales enablement tools and we continue to help companies improve communication with all of our solutions. 

Discover why CloudApp should be used by programmers to communicate better today.

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