Most Common Array Interview Problems

Array manipulation problems are some of the most frequently tested topics in technical interviews. Mastering common patterns and approaches for solving these problems can significantly improve your chances of success. Here’s a list of some of the most popular array interview problems, from the most common to the least common that have reportedly asked these questions in interviews.

1. Merge Sorted Array

• Problem: Merge two sorted arrays into one sorted array without using extra space (i.e., in-place).
• Common Approach: Use two pointers starting from the end of each array to merge efficiently.
• Frequently Asked By: Amazon, Google, Microsoft
• Link: Merge Sorted Array

2. Remove Element

• Problem: Remove all instances of a given value in-place and return the new length of the array.
• Common Approach: Use a two-pointer technique to overwrite occurrences of the target element and shift remaining elements forward.
• Frequently Asked By: Apple, Amazon
• Link: Remove Element

3. Remove Duplicates from Sorted Array

• Problem: Remove duplicates from a sorted array in-place, returning the length of the unique elements.
• Common Approach: Use two pointers, one for traversing and one for placing unique elements.
• Frequently Asked By: Google, Facebook, Microsoft
• Link: Remove Duplicates from Sorted Array

4. Majority Element

• Problem: Find the majority element (appears more than n/2 times in an array).
• Common Approach: Use the Boyer-Moore Voting Algorithm or a hashmap to efficiently identify the majority element.
• Frequently Asked By: Facebook, Amazon, Google
• Link: Majority Element

5. Rotate Array

• Problem: Rotate the elements of an array by k steps to the right.
• Common Approach: Reverse the entire array, reverse the first part, and then reverse the second part. This approach achieves rotation in-place with O(1) extra space.
• Frequently Asked By: Amazon, Microsoft, Google
• Link: Rotate Array

6. Best Time to Buy and Sell Stock

• Problem: Given an array of prices, determine the maximum profit by choosing the best day to buy and the best day to sell.
• Common Approach: Track the minimum price and calculate potential profit at each step to find the maximum achievable profit.
• Frequently Asked By: Google, Facebook, Apple, Amazon
• Link: Best Time to Buy and Sell Stock

7. Jump Game

• Problem: Determine if you can reach the last index of the array starting from the first index, given that each element represents your maximum jump length.
• Common Approach: Use a greedy approach to keep track of the farthest reachable index as you iterate through the array.
• Frequently Asked By: Facebook, Google, Amazon
• Link: Jump Game

8. H-Index

• Problem: Calculate the H-Index for an author based on their publication citations.
• Common Approach: Sort the array, then find the H-index by counting the number of publications with citations greater than or equal to a certain threshold.
• Frequently Asked By: Google, Microsoft, Amazon
• Link: H-Index

9. Text Justification

• Problem: Format a list of words into lines of a fixed width with left and right justification.
• Common Approach: Use a greedy approach to gather words for each line, then distribute spaces between words for full justification.
• Frequently Asked By: Google, Facebook, Microsoft
• Link: Text Justification

How to Use This List for Interview Preparation

These problems cover a variety of array-based concepts, from basic manipulation to complex problem-solving techniques. Start by understanding the problem requirements and common solution patterns, such as two-pointer techniques, greedy algorithms, and in-place modifications. Practicing these questions will help you build the foundational skills needed to tackle array problems commonly asked in FAANG interviews.

This list serves as a solid foundation for your array problem preparation, so start practicing and work your way through these challenges to be well-prepared for technical interviews.