# How to Answer Algorithm Interview Questions

As you prepare for your algorithm job interview, it’s important to practice common algorithm interview questions you might be asked. Knowing these common questions will help ease stress, help you prepare your answers and allow you to anticipate any difficult questions you may be presented with. Here are some common algorithm interview questions and tips to help your interview preparation and chances of landing a position in this field.

## Why interviewers ask specific algorithm interview questions

When interviewers ask you questions, they’re testing your knowledge and expertise in a particular field. If you’re interviewing for an algorithm position, interviewers are hoping to gauge your coding skills, problem-solving skills and more. Your answers to these questions will help them determine whether or not you meet the job qualifications.

Prior to your interview, consider looking over the job posting. The job description will have a list of qualifications that the employer is looking for in particular. Typically, algorithm interviewers will ask you questions based on the job requirements to ensure you’d be a good candidate for the role.

## Common algorithm interview questions

Here are some interview questions you might receive during an algorithm interview:

### What is an algorithm?

Interviewers ask this question to ensure you know the most fundamental aspect of your future job. They are using it to gauge your clarity on the role and algorithms in general. When you answer, do your best to be clear and concise while showing an overall understanding of what an algorithm is.

**Example:** ‘An algorithm is a computational procedure that is used to either solve various problems or perform a computation.’

### Why should an algorithm be used?

This question is asked to ensure you know the ins and outs of algorithms, their uses and their benefits. Though there are several benefits to consider, limit your answer to a few and expand upon each of these so as not to get too wordy. Make sure to focus on the benefits you know best when you answer.

**Example:** ‘An algorithm provides many benefits. It compares the algorithm’s performance to other techniques, reduces the design cost and allows the designer to better understand the program’s flow, among other benefits.’

### What is an asymptotic notation?

Interviewers may ask this when they want to know whether or not you have a clear understanding of this language. As a designer, it’s important that you’re able to understand how an asymptotic notation works. Consider answering with an asymptotic notation’s relation to growth rate and the three common types of asymptotic notations.

**Example: **‘An asymptotic notation is a tool that allows designers to analyze an algorithm’s running time. Three common asymptotic notations include the θ notation, Big O notation and Ω notation.’

### What are the algorithm analysis criteria?

As a designer, it’s important to understand the efficiency of an algorithm. This is because the choice of an algorithm depends upon two criteria. Demonstrate your knowledge of this by stating both factors. You can also provide the definition for each to highlight your skills in this area.

**Example:** ‘One factor of algorithm analysis is time complexity which refers to the quantification of time by an algorithm or set of code to run as a function of the input length. The other is space complexity which is the amount of storage or memory an algorithm needs.’

### How do divide and conquer algorithms work?

An interviewer may ask you about particular algorithms to gauge your knowledge of each. One such algorithm is the divide and conquer algorithm. When you answer this question, make sure you don’t confuse it with another. It’s also important to show your understanding by stating this algorithm’s process.

**Example: **‘Divide and conquer is an algorithmic paradigm that aims to solve a problem using three basic steps: divide, conquer and combine. First, the problem will need to be divided into smaller subproblems. Next, each will need to be solved independently. Lastly, all of the answers will be combined into a single solution. Some divide and conquer algorithms include quicksort, binary search, closest pair of points and merge sort.’

### What is a Hash Table?

An interviewer may ask you this when they’re trying to gauge your skills with a Hash Table. When you answer, make sure you understand how it works and what its main function is.

**Example:** ‘A Hash Table is a data structure that can map keys to certain values. It also stores data associatively and in an array format. A hash function is used to assign keys to a bucket.’

### What is dynamic programming?

This question is used to test your knowledge of dynamic programming and problem-solving in relation to algorithms. When you answer, make sure you know the function of this paradigm. It can also be beneficial to include an example of dynamic programming.

**Example:** ‘Dynamic programming is a paradigm that’s used to solve problems by way of solving every intermediate subproblem once and saving the answer in a table or array. In other words, it stores these answers to be reused for solving the problem at large.’

The more questions you’re prepared to answer, the better chance you’ll have for a successful algorithm interview. Be sure to consider how you would answer these common algorithm interview questions in your own words so you can be confident during the interview.