11 Binary Search Interview Questions (With Example Answers)

Updated 30 September 2022

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The information and technology sector has grown exponentially in the last two decades, and organisations are constantly updating their information technology services (ITS), software, telecommunications, hardware, data and information systems. Companies typically want to assess a potential employee's knowledge of fundamental computer science concepts and their understanding of them as a developer. If you are looking for a position in the IT sector, you may encounter a variety of binary search interview questions. In this article, we list some common binary search interview questions and the appropriate answers to help prepare you for your interview.

11 Common Binary Search Interview Questions

To answer binary search interview questions, it is vital to have a comprehensive understanding of the concepts as related to your industry. Reviewing these basic and advanced interview questions with detailed answers can help you with your job interview:

1. What is a search algorithm and what types are there?

This is a straightforward question that an interviewer asks to evaluate your understanding of the fundamentals. Some employers may ask you to simply list types of algorithms, while others may ask you to extensively explain each type. You may want your answer to highlight your understanding in an informative manner.

Example: 'Search algorithms identify or retrieve a data structure element. Depending on the kind of operation, the algorithms may be a sequential search or interval search. Binary search is an interval search algorithm, whereas linear search is a sequential search algorithm.'

2. What is a binary search?

An employer may ask you this question to assess your basic understanding of the concept before evaluating your knowledge in more depth. In your answer, briefly define binary search in an informative manner. You may want to list the variants of binary searches to demonstrate your knowledge.

Example: 'Binary search is a popular search technique. Its algorithm efficiently finds an element or an item from a list of items. Its working principle is that it divides the data in half and runs this process until it detects the desired value. It is also known as a logarithmic search.'

3. What is the difference between binary search and linear search?

This binary search interview question ascertains your understanding of the key differences between types of search algorithms. When you answer, briefly define these terms. You may want to use a simple example to highlight the difference.

Example: 'Binary search is an algorithm that locates an element within an array in a recursive manner, whereas linear search locates an element within an array that may be in a random order in a sequential manner. For a larger array, a binary search takes less time than a linear search.'

4. What is the process of binary search?

An employer may ask this question to gauge your understanding of the sequence of steps these types of algorithms follow when they run. Your answer needs to reflect your knowledge of the binary search process. To answer this, explain these steps simply and clearly to the employer.

Example: 'Following the execution of the algorithm, the process starts by dividing the sorted array of data in half and locating the middle element. It then compares the key value with that element. If the key value is less than the middle element, then the algorithm analyses the upper values for the match. If the key value is greater than the middle element, then it analyses the lower values for the match.'

5. What are the drawbacks of binary search?

This question assesses your understanding of the scope of the search algorithm. This answer explains the limitations of binary search in comparison with the usage of other types of search algorithms. To answer this question, briefly explain the drawbacks of binary search.

Example: 'One of the main drawbacks of binary search is that the elements are in a sorted array. Its code structure is more complex than sequential search algorithms and requires more stack space.'

6. What are the advantages of binary search?

Binary search is an effective algorithm for finding a single item in a sorted list of items. The interviewer may ask you to highlight some of the advantages of binary search over other types of search algorithms. You may want to highlight your understanding in a brief and informative manner.

Example: 'The binary search is a very efficient way to find an element or key-value from large chunks of data in a sorted array. It takes less time to narrow down the search because of this information.'

7. Where is binary search used in practice?

Employers may design some binary search interview questions to gauge your understanding of binary search in terms of its applicability. You may wish to briefly explain its conventional uses and what binary search offers in terms of solving real-time issues. The best response is specific, accurate and employs technical terms.

Example: 'You can use the binary search to efficiently find an element or key value from large chunks of data in a sorted array. Additionally, you can use it to debug a piece of code that is linear by locating the step where the code starts to run a different result than its target.'

8. What are time and space complexities?

An interviewer may also ask you this question to determine your knowledge of key concepts that are associated with binary search. This question helps them understand how well you understand the fundamental concepts and whether you can answer this question clearly. When answering, you can also list the types of analysis that different types of search operation algorithms encounter.

Example: 'The time complexity of an algorithm represents the amount of time necessary to run that algorithm as a function of the input length. The algorithm's space complexity reflects the required amount of space to run the algorithm as a function of the length of the input.'

9. Why is the time complexity of binary search O (log n)?

Interviewers may ask this question to assess your theoretical knowledge about the principles of binary search and its derivation. Your response can reveal how well you understand the fundamentals of binary search. You may wish to explain this with the help of an example to better communicate your point.

Example: 'Since binary search involves dividing a sorted array in half and comparing the key value with the middle element and then recursively running it, the logarithmic function applicable here would be O (log n).'

10. Could you provide a simple example to explain the time complexity of linear search and binary search?

This question tests whether you understand the fundamentals of the subject. The interviewer may ask this question to determine your understanding of the concept of time complexity in a simple case scenario. The best response is specific, accurate and uses the appropriate technical vocabulary.

Example: 'In of a group of 50 people, you give a 100-rupee note to one individual. In the case of linear search, retrieving the note requires asking one person if they have the note and then asking that individual about the rest until its discovery. You can represent this as O (nÂ°). In the case of binary search, you would divide the group in half, identify which group has it and then take that group and divide it in the same manner until you discover the note. You can represent this as O (log n).'

11. What are the different types of binary search?

As the interview proceeds, the interviewer may test your knowledge of different types of binary search. This question assesses your knowledge of the minor variations in the logic of these searches while implementing the code. Explain the different variants of binary search in simple sentences.

Example: 'While most primary use cases contain a key, some variants of binary search are cases that use the index of the first occurrence of a key, the index of the last occurrence of a key, the index of the least element greater than the key or the index of the greatest element less than the key.'

Tips For A Successful Interview

Here are some additional tips to help you prepare and build your confidence for a constructive interview.

Conduct additional research on the company and its industry position. Know some basic facts about its competitors, market advantages and internal policies.
Practice answering commonly asked interview questions and rehearse them out loud with a mentor or colleague.
Have extra copies of your resume when you go to your interviews and organise all your documents. This may be useful in case of misplacement or change in directives.
Arrive at the interview at least 20 minutes early. Punctuality is an attribute employers look for in a candidate.
Wear an appropriate outfit that matches the company's professional dress code.
Use positive body language, including good posture, clear speech, maintaining eye contact and a firm handshake.
Prepare a set of constructive and thoughtful questions to ask the interviewer in case you get an opportunity to do so. Some sample questions could be: 'What qualities can help me to succeed in this role?', 'What are the opportunities and challenges I can expect in the role?', 'Can you describe a typical workday?', 'Is there any advice you would give if I earned the opportunity to work for you?'.
Send a follow-up email within 48 hours of your interview to thank the interviewer or the hiring manager for their time.

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