40 Important Array Interview Questions (With Sample Answers)
Updated 30 September 2022
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Programming roles involve a high level of technical understanding of data structures, programming languages and algorithmic functions. Understanding array structures and how they work within a code is one of the most fundamental abilities for programmers. When applying for programming jobs, you may encounter questions concerning arrays and their use during interviews. In this article, we share 40 common array interview questions and provide a few example answers for your reference to help draft your responses.
10 General Array Interview Questions
General array interview questions can help an interviewer understand your interest in the role. Some general questions an employer can ask are:
What are your career goals for the next five years?
Do you have any questions regarding this role?
What do you expect from this job?
Why do you want to work with us?
Describe the ideal environment where you wish to work.
What do you hope to accomplish in the first three months on the job?
What encouraged you to seek opportunities in this field?
What is your favourite programming language and why?
What skills do you have that differentiate you from others?
What is your desired salary range?
Related: How To Answer The Salary Expectation Question In Job Interviews
10 Questions About Experience And Background
Hiring managers often ask candidates the following questions about their educational background and professional experience:
How can your previous work experience help you in this position?
What is the most enjoyable programming job you have had in your career so far?
How do you stay motivated during complex projects?
How do you improve your technical skills?
Describe the toughest challenge you have experienced in your development career so far.
Share your experience with Java programming.
In an organisation, who is responsible for updating indexes?
Have you ever had a project run over budget?
What is your usual project management process?
What certifications or training do you have that can you perform this role better?
Related: 10 IT Certifications (With Qualifications And How To Prepare)
11 In-Depth Questions
Here are a few common in-depth interview questions related to arrays:
What is an array data structure?
How does the quicksort algorithm sort an integer array in place?
How can you find duplicates in an array?
Is it possible to change the array size during the run time?
What is the default value of an array?
Explain the anonymous array.
Explain the steps for declaring multi-dimensional arrays in Java.
Do we have 3-dimensional arrays in C?
How do arrays and ArrayLists differ?
How do you intersect two sorted arrays?
How do dynamic arrays work?
Related: What Is Object-Oriented Programming Language? (With Basics)
9 Array Interview Questions With Sample Answers
Here are nine common array-based interview questions and sample answers to help you prepare for your next interview:
1. How do you reverse an array?
Hiring managers may ask how to reverse an array to test your basic knowledge of arrays and your ability to manipulate them in your code. In your response, you can explain how to reverse arrays in a step-wise manner and share an example if required.
Example: "There are multiple ways of reversing an array. One option is to establish a reverse function and insert a new array with the same parameters and data as the original to create a temporary array. Swapping the components within the original array is another option. This is done by changing 1 for n, 2 for n -1 and so on for each item in the array. Using the collection reverse list method to convert the array to a list is another way."
2. How does an array differs from a linked list?
An interviewer may ask you to explain the fundamental distinctions between an array and a linked list to see if you have a basic understanding of data structures and when to use them. A detailed response can help demonstrate your ability to reason when to use a specific structure.
Example: "An array is a pre-defined structure that you cannot change. A linked list provides more flexibility and allows for size changes. A linked list can also extend indefinitely, but arrays cannot. In terms of memory, linked lists are more adaptable. A linked list can use distributed memory, whereas an array can only use contiguous memory. Linked lists are ideal for sets that change in size. An array is better for fixed sets and is more useful for rapid data retrieval when using an index."
3. What are the pros and cons of using arrays?
This question helps the hiring manager evaluate your understanding of arrays and ability to reason logically. You can demonstrate your expertise by explaining when arrays are useful and when it is best to utilise another way in your response.
Example: '"Arrays can sort several elements simultaneously and set up other data structures like stacks, queues and trees. Accessing elements via the index is a significant advantage of utilising an array. As arrays have a fixed size, I only use them when I know the size of the data set before writing the array."
4. How do you identify a missing integer in an array of 1 to 100?
Interviewers ask this question to test your understanding of functions that programmers use to modify or troubleshoot arrays. As the answer can change depending on the particular items or structure of the array, this question can also test your reasoning abilities. Providing solutions for all scenarios can demonstrate your adaptability and expertise to the interviewer.
Example: "First find the sum of the series with a function, then subtract the result from the sum of the complete series. For this particular question, find the sum of all integers from 1 to 100 using the formula n(n+1)/2 and which is 5050 in this case. The missing integer would be the total of 5050 minus the sum of all array items."
5. How do you remove a particular element from an array?
This is a relatively simple question that interviewers can ask to assess your knowledge and problem-solving skills. As removing an element from an existing array is not direct action, the interviewer expects you to propose an alternative solution in your response.
Example: "As arrays are fixed sets with fixed sizes, it is impossible to remove elements from the original array directly. Creating a new array is the best approach to removing an element. To do this, simply include copies of the first array's elements in this array while excluding the element you want to remove."
6. How can you get the index of an array element?
Hiring managers may ask you to explain the steps involved in getting an element's index to assess your knowledge to write code and use the appropriate functions. You can showcase your skill level and experience by explaining multiple methods briefly in your response.
Example: "A linear or binary search can find the index of an array element. A linear search function starts with the first element and works through each item until it finds the target element's match. It returns the index once it has found the matching element. A binary search divides the array in half periodically until the median of the interval matches the required element and returns the index. You can use a binary search function if the array is sorted. A linear search is usually more efficient when the array is not sorted."
Related: What Is The Tree Data Structure? (With Advantages And Types)
7. How do you merge two sorted arrays into one sorted array?
The hiring manager may assess your knowledge of more sophisticated coding functions, such as merging arrays. Describing this process in your answer can help demonstrate your programming knowledge.
Example: "With two sorted arrays, you can use a more efficient merge sort method. With this method, you can create an auxiliary array with the size as the total size of both arrays and insert the merge element in this array. To do this, traverse both the array simultaneously using the pointers and choose the smallest elements in both the array and put it into the auxiliary array."
8. What steps would you take to rotate a 2D array?
To assess your technical understanding, interviewers may ask you about 2D arrays. Giving a detailed answer and utilising the correct terminology for arrays, matrices and rings can demonstrate that you understand programming functions and data structures.
Example: "Starting with the outermost element and rotating each ring of elements sequentially, you can rotate a 2D array or matrix. To rotate a ring, start by moving the top row components, then the last column, then the bottom row, and lastly, the first column. You repeat this procedure for each ring or make this rotation multiple times using loop functions until you get the desired result."
9. How does searching differ from sorting?
This question tests your fundamental knowledge of array terminology and your ability to distinguish between these two key concepts. In your response, you can define searching and sorting and explain how they differ from one another.
Example: "The term 'searching' refers to looking for a certain element inside an array that meets certain criteria. Whereas 'sorting' refers to changing the order of the items in an array to ascending or descending based on a defined parameter."
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