Common coding interview mistakes to avoid

Coding interviews can be nerve-wracking—even for experienced developers. The pressure to perform perfectly under time constraints often leads to mistakes that could have been easily avoided with proper preparation. Even the most seasoned developers may experience anxiety due to the fear of completing tasks inefficiently and the worry of making mistakes. Many bright applicants struggle during the interview process, facing challenges such as:

• Lack of practice with behavioral questions

• No research on the company and its culture

• Inadequate communication

• Poor time management

• Lack of technical preparation

Understanding these common issues—and how to fix them—can give you a competitive edge, turning weaknesses into strengths. With proper planning, practice, and strategy, interviews can become less Intensive and more manageable. In this blog, we will explore common mistakes and challenges that candidates face during the interview process and provide tips on how to avoid them.

Pre-interview mistakes#

Candidates often make mistakes even before appearing in the coding interview. Some of the common pre-interview mistakes are as follows:

1. Skipping mock interviews#

Appearing in a coding interview without taking mock interviews can leave you unprepared for the actual interview environment. Mock interviews simulate a real interview’s conditions and identify improvement areas. They also provide an opportunity to simulate the pressure of a real interview. Without taking mock interviews, you will be unfamiliar with the interview format. The lack of practice will result in low confidence and poor time management.

Here’s how you can avoid this:

• Mock interviews should be regularly conducted to seek feedback on performance and identify and improve areas of weakness.

Mock interviews have different types; you can choose one at your convenience. Some of the common types of mock interviewers are listed in the table below:

2. Not researching about the company#

This is perhaps the most common mistake candidates make. Appearing in an interview without researching the company indicates that you are not interested in the company and its culture. You won’t be able to answer questions about the company’s value, products, and achievements.

To avoid this situation, always make sure to:

• Research the company’s website and social media profiles to learn about its activities and latest achievements.

• Read about the company’s goals and mission statement.

• Get information about the type of products or projects the company is developing.

Behavioral mistakes#

A candidate’s behavior during the interview can significantly impact the impression they make on the employer. The behavioral interview is as important as the technical part. Some of the common behavioral mistakes are as follows:

Being impolite#

Acting impolitely gives a long-lasting bad impression to the interviewer. Professionalism is the key to having a successful interview. In addition to your technical skills, interviewers evaluate your behavioral skills about the company culture. Impoliteness indicates a lack of respect for coworkers. The following tips are helpful to avoid this behavior:

• Throughout the interview process, treat everyone you interact with with respect.

• The interviewer may ask you basic or obvious questions, but you should stay calm and give them satisfactory answers.

• Being polite during an interview shows that you can handle uncomfortable situations in the work environment.

Lack of preparation#

If you appear in an interview without the required preparation, it will badly impact your performance. It indicates that you are uninterested in this role or position and do not respect the interviewer’s time.

Before the interview, do the following:

• Read the job description carefully and prepare for the related questions.

• Search for top interview questions related to that role and prepare them. For example, if you are appearing for a coding interview, some of the top questions are:

  • What are the data structures?

  • What is the biggest problem that the linked list has solved?

  • What is a stack used for?

  • What is the time complexity of an algorithm?

  • Can you explain how binary search works?

Educative offers an excellent course that helps with acing behavioral interviews. It has an extensive list of questions. You can check the course below:

Technical mistakes#

The technical part of the interview is the most important part of the hiring process for a job role and is the deciding factor in selecting a candidate. A mistake can create a negative impression and impact the candidate’s performance. The following is a list of common technical mistakes and how to avoid them.

1. Not understanding the problem#

To solve a problem, you must understand it first. Diving straight into the code before fully understanding the problem is a common mistake candidates make during a coding interview. Not spending time understanding the problem transmits a bad signal to the interviewer that you are not a suitable candidate for a particular role.

To overcome this situation:

• It is important to understand the problem fully.

• Think out loud about the problem, so the interviewer should know your approach to solving a problem.

• Understand the key parts of the problem by asking clarifying questions from the interviewer.

For example, for the Reverse Words in a String problem, you may be given the following problem statement:

You can ask the following questions to the interviewer:

• Can the input string contain newline characters?

• Can we have an empty string as an input?

• Should we return the original string or modify the original?

• Do you have a specific edge case you want me to cover?

• Should we handle the trailing and leading spaces?

2. Poor time management#

Effective time management is critical in coding interviews. Many candidates take too long on one part of the problem, leaving them with little to no time to finish the other parts. This results in missing the chance to demonstrate their abilities. Time pressure can cause anxiety, leading candidates to get stuck even on minor details. This indicates that the candidate is not good at time management.

To tackle this situation:

• Break down the problem into smaller parts and allocate time to each part.

• Allocating time efficiently to different parts of the problem is necessary to demonstrate the ability to handle real-world tasks within deadlines.

If you have 30 minutes to solve a given problem in a coding interview, it is important to carefully allocate time to understand the problem, write its solution, and test it. Here is how you can divide the 30 minutes:

• Understanding the problem (5–7 minutes): Use this time to read the problem statement and its requirements carefully. Also, write down the constraints and edge cases.

• Planning and implementing the solution (15–18 minutes): Write the solution’s code. While writing the code, it is important to consider the constraints and edge cases so you can handle them well.

• Testing the solution (5–8 minutes): Take a few minutes to test your solution before presenting it to the interviewer. Test your code with different inputs, including edge cases, and modify the code if necessary.

3. Neglecting edge cases#

The solution you have written may work well with general cases but not special ones. The interviewers are more interested in solutions that can manage all potential inputs. The solution may work unexpectedly or even break when testing on edge cases. Handling edge cases demonstrates an in-depth knowledge of the issue and the ability to anticipate potential pitfalls.

To overcome such issues:

• Consider all potential scenarios and evaluate solutions, keeping them in mind.

• Consider the inputs that might cause the code to break.

4. Overlooking the time and space complexity#

When writing a solution to a problem, ignoring the time and space complexity will make the code unable to handle large inputs. Interviewers always seek candidates who can design efficient solutions that scale effectively. Optimizing time and space complexity is important for developing code that performs well across different scenarios. Ignoring them indicates that you don’t know how to solve problems enough.

Remember to:

• Understand the complexity of time and space while writing the solution.

• Discuss the complexities of your solution with the interviewer, and explain why you came up with this complexity.

• Discuss with them how you can even reduce the complexity.

5. Not writing readable code#

Code readability is vital for collaboration. Interviewers evaluate your code for accuracy, clarity, and organization. Code readability is highly valued in professional environments because hard-to-read code can be difficult to debug and maintain. Not writing readable code will negatively impact your performance, even if your code works flawlessly. Let’s take an example of a code that works perfectly but is hard to read and understand. The following is a poorly written solution to the Two Sum problem:

We can see that although the code works perfectly, it is not easy to understand. It has one-letter variable and function names, which do not convey any meaning. Let’s now see a human-readable version of the same code:

The code above uses the full names of variables and functions and follows coding conventions, which makes it easy to read and understand.

To write better and readable code:

• Follow coding standards and best practices.

• Use meaningful variable names and consistent indentation, and include comments where necessary.

• Use familiar design patterns to demonstrate that you know the industry’s best practices.

• Remember that you are not writing the code for the machine but also for the human.

6. Lack of the coding pattern knowledge#

You will likely write an inefficient solution if you solve a problem without a coding pattern. A solid understanding of the coding patterns is required to appear in coding challenges and interviews. Solving a problem without coding a pattern will take much longer than usual.

The following are the reasons why you should learn coding patterns:

• Learning about coding patterns is necessary for solving problems.

• Coding patterns help you understand the problem quickly and write consistent and efficient code.

• Coding patterns include best practices to solve a problem.

7. Lack of communication#

Silent coding is not a good approach in a coding interview. Communication is important to effectively convey your approach to solving the problem. Interviewers do not want to sit and watch you solve the problem; they want a meaningful conversation.

To avoid such situations, keep in mind the following points:

• You should communicate with the interviewer by asking relevant questions and discussing your approach to solving the problem.

• Your thought process behind your decisions should also be clear to the interviewer.

• Communicating well with the interviewer will also let them advise you if they think you are going off the track.

8. Not asking for help#

It is okay to be stuck in a problem but not to stay stuck and not ask the interviewer for help. Not asking for help can signal that the candidate might struggle with effective communication, which is the key part of a collaborative work environment. Without seeking guidance, the candidate might spend too much time stuck on a particular issue, leading to inefficient use of the interview time.

To avoid this issue:

• The candidate must seek help from the interviewer if they get stuck somewhere in the problem.

• Ask only for the information required to get out of the blocking zone and avoid over-asking.

• Ask minimal questions, indicating that the candidate can work with little supervision.

Conclusion#

By avoiding common mistakes and following a structured plan, you'll be well-prepared to excel in coding interviews. Rather than feeling anxious, you'll tackle the process with confidence—and maybe even a sense of excitement. With the right approach, you'll turn interviews into opportunities to showcase your skills.

Next steps#

Now that you're aware of common coding interview pitfalls and how to avoid them, it's time to put this knowledge into practice. Tailor your preparation to focus on your specific areas of improvement, whether it's mastering data structures, improving problem-solving techniques, mastering algorithms, or refining your coding patterns. Consider using Educative's AI-powered interviewer for a mock interview. Also, consider the resources below that align with your learning style, so you can confidently tackle your next interview and land the job you want.