10 Coding Interview Mistakes You Must Avoid to Get Hired
Ever spent weeks practicing coding problems, only to freeze during the actual interview?
You're not alone. According to InterviewPlus, approximately 80% of candidates fail coding interviews, often due to preventable mistakes rather than a lack of technical knowledge.
The truth is, knowing how to solve problems is just half the battle. Interviewers also assess your approach, communication skills, and composure under pressure. Even a minor misstep can cost you the offer, regardless of whether your code is correct.
In this blog, we'll break down the most common mistakes candidates make during coding interviews and how you can easily avoid them to boost your chances.
What Is Usually Asked in a Coding Interview?
You will be asked to do more than write code in the coding interview. The interviewer also assesses your problem-solving skills and how you handle situations under pressure.
Here's what you can expect in your next coding interview:
- Data Structures and Algorithms: Coding problems on arrays, strings, trees, graphs, dynamic programming, etc.
- Problem Solving Skills: How you break down a tough problem and find a working solution.
- System Design (for senior roles): Designing scalable systems like a URL shortener or a chat app.
- Behavioral Questions: Discuss your past projects, teamwork, and problem-solving experience.
- Coding Skills: Writing clean, efficient, and bug-free code in your preferred programming language.
Each round is designed to check not just your coding ability, but also how clearly you explain your thoughts and how you approach challenges.
10 Common Coding Interview Mistakes You Must Avoid
When it comes to cracking the coding interview, even experienced professionals can struggle if they make small mistakes like not explaining their thought process properly or skipping edge cases. So, if you want to ace the interview and stand out, you should avoid the following common mistakes during your coding interview.
1. Not Understanding the Coding Problem Clearly
The most common mistake every interviewee makes is not discussing the problem statement clearly. When the interviewer asks the question, they directly rush to solve the problem or write a code to stand out and impress the interviewer by quickly solving the problem. At the end, they become confused about the questions asked and end up providing the wrong solution, which makes a bad impression.
Here is what you should do to clearly understand the problem or question:
- Ask the interviewer a question or problem again if you haven't understood it clearly. Trust me, Interviewers don't mind explaining you questions 2 to 3 times.
- Clearly ask for input/output format.
- Also, discuss if there are any constraints to follow.
- Confirm you understand the problem clearly by restating it in your own words.
Note: Once you understand the problem clearly, you can jump into writing the code.
2. Lack of Communication
The interview is not a game of questions and answers, but it's all about continuous discussion.
Once the interviewer gives you a problem to solve, don't just stay silent for 10 to 15 minutes while thinking the solution approach, because the interviewer can't read your mind. So, if you stay quiet, they won't be able to know whether you are using the right approach to solve a problem, or are stuck in between.
Even enginners don't work in silos; but they work in teams. So, continuous communication can demonstrate your ability to discuss problems and ideas and work in teams.
Here is how you should communicate while solving the coding problem:
- Communicate the solution approach that you are going to implement. If possible, explain the brute-force approach first and then the optimized approach.
- Once you start writing the code, keep explaining each part of the code.
- When you get stuck, ask for help. The interviewer will definitely help you and suggest the right approach.
However, you don't need to narrate each line of the code, but keep the discussing important parts. So, the interviewer can understand the overall solution approach.
3. Overcomplicating the Solution
Keep a simple rule in your mind: "If you have multiple solutions in your mind, use the simplest one and don't go for the fancy solution to show yourself clever."
For instance, if the interview has given you the "Two Sum" problem to solve. Three approaches might come to your mind to solve the problem:
-
- Using Sorting + Binary search
-
- Using Sorting + Two Pointer
-
- Using HashMap
Here, the third approach is the simplest and time/space efficient. With other approaches, the candidate might get stuck or take more time to solve the problem.
4. Ignoring Edge Cases While Solving a Coding Problem
Suppose your code works well for normal inputs, but when the interviewer tests it with the empty input, it fails. Ops! How to overcome this mistake? Well, follow the checklist below:
- Discuss edge cases with the interviewer after discussing the problem statement. It could be:
- Null values
- Empty arrays or strings
- Unique entries
- Maximum and minimum values
- While implementing a solution, you can think about how to handle edge cases.
By writing a code that works for all test cases, you can really impress your interviewer, as it shows your ability to consider all scenarios while writing code.
5. Not Considering Time and Space Complexity
Many candidates just focus on writing a solution that comes first to their mind; they don't care whether the solution is a brute-force or an optimized one.
At the end, when the interviewer asks something like, "will this solution work for 10<sup>6</sup> input?", and they hesitate to say no, which shows a weak understanding of the candidate.
In real jobs, ignoring time and space complexity can lead to slow features, server overload, or wasted cloud costs. So, you must consider the complexity of the solution while solving a coding problem in the interview.
6. Poor Time Management During the Interview
Of course, everyone faces time pressure in the interview, as you need to prove yourself in 45 to 60 minutes. Few candidates spend a lot of time planning the solution, and then they realize that very little time left to implement the code.
To avoid mismanagement of time, candidates can follow a time plan like below:
- 5–7 mins: Understand and ask clarifying questions.
- 8–10 mins: Plan your approach carefully.
- 20–25 mins: Code while explaining your steps clearly.
- 5–8 mins: Test with different cases and discuss optimizations.
7. Lack of Professionalism
Skills can be trained, but attitude is hard to fix.
It doesn’t matter how smart you are; if you behave rudely or show a bad attitude to the interviewer, it can kill your chances of getting hired.
Companies don't just hire coders who can write code, but they also look at their soft skills, like whether the candidate is a team player and gives respect to everyone.
Here is how you can stay polite during the interview:
- Don't interrupt the interviewer when they are talking or asking a question. Listen to them carefully, and once they stop, ask your questions.
- Don't do false arguments.
- Thanks to the interviewers for the tips, even if you knew the answer.
- If you do not agree with the interviewer on anything. Politely ask for permission to share your opinion, like "May I share a different perspective?"
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8. Ignoring the Job Requirement
Many candidates just go for the interview without looking at the job role requirements. For instance, the company might be looking for a candidate who has experience in system design, but if you only prove that you're a coding expert, you fall short. Similarly, suppose the company is looking for a candidate who has experience in working with "large datasets", but you never talk about memory efficiency, and so on. In that case, the interviewer can assume that you're not the right fit for the particular job role.
How to align with the job role:
- Read the job description carefully before you attend the job interview.
- Try to link your answers to the job requirements during the interview.
- Prove that you are perfect for the particular job role.
9. Not Doing Research About the Organization
If you're one who never does research about the organization before going to the interview, never make this mistake again.
It is always true that the interviewer asks company-related or role-specific questions to test your preparation. Even some interviewers ask direct questions like "Do you know our products or what services we are providing?". In such scenarios, it makes a bad impression on you if you don't know about the company.
Golden Tip: If two candidates perform equally in coding, the one who understands the company usually wins.
So, take 10 to 15 minutes to go through the company's site and learn more about it before you attend the interview.
10. Assuming You’ll Be Asked Only Coding Questions
The biggest mistake is assuming that you will be asked only to solve coding problems during the interview, but that's not right.
Interviewer can also ask core computer science concepts and non-technical questions, such as:
- OOPs related concepts: Revise Object-oriented programming concepts, like "Inheritance," "Polymorphism," "Encapsulation," "Diamond problem," etc.
- DBMS Concepts: Based on the job role, the interviewer can also ask candidates to write SQL queries or ask theoretical questions related to DBMS.
- Non-technical questions: The Interviewer can ask questions like "Tell me about yourself," "Why do you want to join us?", etc.
So, always be ready to answer theoretical questions related to core concepts of computer science.
Bonus Tips to Shine in Coding Interviews
Avoiding mistakes is step one. But if you want to stand out and make a strong impression, here are some smart tips you can apply:
- Practice Enough Coding Problems: You can practice coding problems on freely available platforms. But if you want a clear roadmap to prepare for the next coding interview, you should enroll in the coding interview patterns course offered by DesignGurus.io. This course will help you master specific coding patterns rather than solving 100s of problems.
- Prepare a 60-Second Intro About Yourself: Before you attend the interview, prepare a 60-second intro and practice it multiple times. Also, don't keep the self-introduction the same; it should be dynamic according to the organization where you are applying and the job role.
- Practice with Mock-Interviews: Practicing with mock interviews will help you avoid mistakes in the real interview.
- Keep Your Resume Stories Ready: Whatever projects or skills you have added to your resume, be ready to talk about them. Make sure you are prepared if the interviewer asks questions about the challenges you faced in a particular project.
- Get Feedback After Interviews (If Possible): Politely ask for feedback if you don’t make it. Even one useful tip from an interviewer can help you improve for the next round.
Discover 8 Tips To Prepare for Coding Interview.
FAQs
It depends on your level. Most candidates spend 1–3 months actively preparing with 1–2 problems daily and regular mock interviews.
Yes. Even if you ace the coding rounds, poor communication or weak soft skills can lead to rejection.
Some do, but it’s usually basic. You might be asked how to design a simple feature or data flow, just to check your understanding.
Stay calm. Think out loud, explain what you’ve tried, and ask for hints if needed. Interviewers often give credit for clear thinking.
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