Arrays are one of the most frequently asked topics in programming interviews. If you’re applying for roles in software development, data science, or any technical domain, expect array interview questions to be on the list. In this blog post, we’ll cover the most common array interview questions, detailed answers, and essential tips to tackle them confidently.
Whether you’re a beginner or brushing up for a senior-level position, this guide is packed with the most important array interview questions and answers.
1. What is an Array?
An array is a data structure that holds elements in contiguous memory locations, accessed using an index.
2. What are types of arrays?
- One-dimensional (1D)
- Two-dimensional (2D) or multidimensional
- Jagged arrays (arrays of arrays)
3. What is the time complexity of accessing an element in an array?
O(1) – Direct access via the index.
4. How do you find the minimum element in an array?
Traverse the array and update the minimum if a smaller element is found.
5. How to find the maximum element in an array?
Iterate and keep track of the largest value encountered.
6. How do you reverse an array?
Swap elements from both ends towards the center.
7. What is a dynamic array?
An array that can grow or shrink during runtime (e.g., Python lists, Java ArrayList).
8. What is the difference between array and linked list?
Array: Fixed size, fast random access.
Linked List: Dynamic size, slower access.
9. How to rotate an array to the right by k steps?
Reverse the whole array, then reverse the first k elements and the rest.
10. What is a sparse array?
An array where most elements are zero or empty.
11. How to remove duplicates from a sorted array?
Use two pointers to overwrite duplicate values.
12. What is a 2D array?
An array of arrays, where each element is itself an array.
13. What is the difference between static and dynamic arrays?
Static: Fixed size.
Dynamic: Can change size dynamically.
14. How to merge two sorted arrays?
Use two pointers and compare elements while inserting into a new array.
15. How do you find missing number in an array from 1 to n?
Sum formula: n*(n+1)/2 - actual_sum.
16. How do you find duplicates in an array?
HashSet approach: Check if an element already exists while traversing.
17. How do you check if an array is sorted?
Traverse and ensure each element is smaller or equal to the next.
18. What is a jagged array?
An array whose subarrays may have different lengths.
19. What is array overflow?
Trying to insert more elements than the declared size.
20. What is time complexity to search in an unsorted array?
O(n)
21. How to search for an element in a sorted array?
Use binary search for O(log n) time complexity.
22. How to delete an element from an array?
Shift all subsequent elements one position left.
23. What are common operations on arrays?
- Insert
- Delete
- Search
- Update
- Traverse
24. What is prefix sum array?
An array where each element is the sum of all previous elements.
25. How to find the kth largest element?
Sort the array or use a min-heap.
26. What is the difference between array and matrix?
Matrix is a 2D array where rows and columns matter.
27. What is the sliding window technique?
A way to move a subset window across the array to solve problems efficiently.
28. Explain the two-pointer technique.
Use two indices that move independently based on conditions.
29. How do you implement a stack using arrays?
Use a variable (top) to point to the last inserted element.
30. What is an associative array?
An array where keys are associated with values (like dictionaries in Python).
31. What is memory layout of an array?
Elements are stored sequentially in a single block of memory.
32. Why are arrays efficient for read operations?
Constant-time O(1) access due to index addressing.
33. Can you implement a queue with an array?
Yes, with two pointers: front and rear.
34. What is circular array?
An array where the end connects to the start (modulo indexing).
35. What is an immutable array?
An array whose contents cannot be modified after initialization.
36. What is difference between shallow copy and deep copy of array?
Shallow: Copies references.
Deep: Copies actual values.
37. What is array segmentation?
Dividing an array into parts to solve problems individually.
38. How do you initialize an array?
Examples:
int arr[5] = {1,2,3,4,5};arr = [0]*5(Python)
39. What is an infinite array?
A conceptual array that can be expanded indefinitely (rare in practice).
40. How to sum all elements of an array?
Iterate and add each element to a sum variable.
41. How to find the longest increasing subarray?
Track current length and update maximum length while traversing.
42. What is difference between vector and array (C++)?
Vector is dynamic, array is static.
43. How to implement hash map using arrays?
Use an array of linked lists (separate chaining).
44. How to find equilibrium index in array?
Where left sum == right sum at a certain index.
45. What is mean and median of an array?
- Mean: Average of elements.
- Median: Middle element after sorting.
46. How to find the majority element?
Use Boyer–Moore majority vote algorithm.
47. How do you partition an array around a pivot?
Dutch National Flag algorithm (three-way partitioning).
48. How to count subarrays with given sum?
Use prefix sum and hashing.
49. How to rearrange array in maximum-minimum form?
Alternate maximum and minimum elements.
50. Can we store different data types in one array?
In strictly typed languages (C, Java), no. In dynamic languages (Python), yes.
📌 People Also Ask:
❓ What is an array interview answer?
An array is a data structure that stores elements in a contiguous memory location. In interviews, candidates may be asked about array operations, time complexities, and algorithms based on arrays.
❓ What is the basics of array?
An array is a linear data structure used to store elements of the same type. Each element is accessed using its index.
❓ What is an array short answer?
An array is a collection of elements stored at contiguous memory locations and accessed using indices.
❓ How to solve any array question?
Understand the problem, determine whether you need to traverse, sort, search, or modify the array, and choose the most optimal algorithm. Use techniques like sliding window, two-pointer, or hashing where needed.
💡 Top 20+ Array Interview Questions and Answers
🛠️ Final Tips to Crack Array Interview Questions
- Practice common array problems on platforms like LeetCode or HackerRank.
- Focus on edge cases like empty arrays, single-element arrays, or negative numbers.
- Learn to use sliding window, prefix sums, and hash maps effectively.
🔍 Conclusion
Arrays are foundational to many programming concepts and data structure problems. Preparing for array interview questions helps build your logic and coding fluency. Practice daily, understand problem-solving patterns, and you’ll be ready to ace any array-related question in interviews.