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How to Answer Data Structure Interview Questions

January 23, 2020

When applying for programming, coding or software development positions, you will likely be given interview questions that focus on data structure. You will be expected to have a firm grasp on concepts and theories that are most relevant to the particular position you are applying for and be assessed on your ability to apply your technical knowledge to real-world scenarios. In this article, you can learn more about data structure interview questions you may be asked along with some tips and example answers.

How to prepare for a data structure interview

When preparing for your data structure interview, it would help to make an assessment of your skills and qualifications. Try to focus on the skills that are most relevant to the job and to the particular company you are applying for. Keep in mind that most questions will probably be highly technical, so brush up on some key concepts. It would also help to draw on your work experience to relate your skills to a real-world work setting or office environment.

Data structure interview questions with sample answers

Here are some questions pertaining to data structure that you may be asked during an interview:

What made you consider a career in creating data structures?

Tip: Interviewers may ask you this question to evaluate your understanding of data structure, what you may be expecting from the position, and why you believe you are an ideal candidate for the job. Your answer should communicate your understanding of how data structure and Big Data contribute to various disciplines and areas of business and how you can contribute to the company’s success if hired.

Example: ‘I have extensive experience in many areas that are integral to Big Data, including quantitative analysis, data mining and algorithm development with a particular focus on SQL/NoSQL. I am also proficient at programming languages such as Python, C++ and Java, as well as machine learning and AI experience. More importantly, I am able to apply these to derive information from a large volume of data, which is the essential function of Big Data.’

This answer demonstrates your knowledge and understanding of the overall industry as well as your understanding of the importance of data structure in many aspects of business and industry. It also showcases your experience and skill and provides a strong argument for why you should be considered for the position.

What are the most important skills to have when working with data structures?

Tip: This question aims to determine your most relevant skills and what value they offer when working with data structures. Before your interview, do some research on the specific technical skills required for the position you are applying for.

Example: ‘When working with data structures, it’s important to have a firm grasp of quantitative aptitude, statistics and linear algebra. Statistics, in particular, is one of the most essential foundations of data science, and it is integral to the understanding of many of the core concepts of data structure, such as random variables, summary statistics, hypothesis testing and probability distribution. Strong problem-solving ability and creativity are other important skills to have in order to excel in this position.’

This answer demonstrates your understanding of the essential skills and technical knowledge that is required for the position you are applying to.

How would you check for cycles in a linked list?

Tip: This question is intended to determine your ability to perform a common coding-related task. It is usually asked in connection with basic linked list questions, such as inserting elements into linked lists or finding the length of a particular linked list. To prepare for this question, make sure you have at least a basic understanding of how to accomplish this task.

Example: ‘I would utilize an algorithm with fast and slow pointers to iterate over the linked list. I would have the fast pointer move toward two nodes and the slow pointer move to one node. If both pointers meet at some point of the iteration, I will know that the linked list contains a loop or cycle. Conversely, I will know that there is no loop if the pointers do not meet.’

This answer showcases your knowledge of an efficient method for detecting the presence of cycles in a linked list, which is a common task for coders and programmers.

What are the most significant benefits and challenges of array data structures?

Tip: This is a common data structure interview question as it involves one of the most fundamental forms of data structure (arrays). Again, the best way to prepare for this question is to make sure you have a basic understanding of array data structures and how they work.

Example: ‘One of the main benefits of array data structures is that they allow for fast O(1) searches. However, this requires knowledge of the index. Furthermore, adding and removing elements from arrays is usually a slow process, because array sizes aren’t changeable after the array is created. Instead of shortening or lengthening an array, it is often more efficient to create a new array and copy all the elements over.’

This answer demonstrates that you have an in-depth understanding of array data structures. Offering more efficient solutions to creating array data structures also shows the interviewer that you are innovative and possess strong problem-solving skills.

How would you find duplicate numbers in arrays that have multiple duplicates?

Tip: This question aims to determine how you will handle a common problem involving arrays. Make sure you understand array data structures and be specific with your response.

Example: ‘I would employ a method that finds the first non-repeated character in one pass using one Set and one List. This keeps repeating and non-repeating characters separate from each other. After scanning through O(n) String, I will be able to identify the relevant character by the O(1) operator or List. Because List is an ordered collection, I will be able to identify the first element with get(0).’

This answer clearly shows your ability to find duplicate numbers in arrays containing multiple instances of duplication, which is a commonly encountered scenario when debugging code. Again, it demonstrates to the interviewer that you understand the subject matter and can find solutions for complex issues.

What is your approach to learning a particular algorithm?

Tip: Your interviewer may ask you this question to determine how you will be able to work with different algorithms and adjust to different scenarios in the course of your work. Show your ability to apply a set of logical principles to the task of analyzing and sorting data to communicate your consistency and professionalism.

Example: ‘With every given scenario, I rely on principles that have worked for other algorithms in the past. I then try to rebuild those algorithms and make modifications and improvements if necessary. I also utilize automated tools to check the code and apply any new principles I have learned to future projects.’

This answer demonstrates a proactive and systematic approach to dealing with different data structures and algorithms. Although the objectives will vary depending on the particular task or project, applying a methodical approach will improve the accuracy of your results and reduce errors.