Cracking DSA coding interviews in 2026 requires mastering fundamental data structures. This guide covers the most asked coding questions on arrays, strings, and linked lists at MAANG and product companies.

Keywords: DSA interview questions 2026, coding interview preparation, array interview questions, string manipulation problems, linked list interview questions, LeetCode preparation

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1. Two Sum Problem

Given an array of integers, find two numbers that add up to a target. Use a hash map to store complements while iterating. Time complexity O(n) and space O(n). This is the most asked coding question across all companies.

2. Best Time to Buy and Sell Stock

Find the maximum profit from buying and selling stock once. Track the minimum price seen so far and calculate profit at each step. Single pass solution with O(n) time and O(1) space. Tests greedy algorithm understanding.

3. Maximum Subarray (Kadane's Algorithm)

Find the contiguous subarray with the largest sum. Kadane's algorithm maintains current sum and maximum sum. Reset current sum to zero when it becomes negative. O(n) time complexity. Fundamental dynamic programming pattern.

4. Reverse a Linked List

Reverse a singly linked list iteratively or recursively. Iterative approach uses three pointers: previous, current, and next. Time O(n), space O(1) iterative or O(n) recursive. Tests pointer manipulation skills.

5. Valid Parentheses

Check if a string of brackets is valid using a stack. Push opening brackets and pop for matching closing brackets. Return true if stack is empty at the end. O(n) time and space. Classic stack problem.

6. Merge Two Sorted Arrays

Merge two sorted arrays into one sorted array using two pointers. Compare elements from both arrays and place the smaller one first. O(m+n) time complexity. Foundation for merge sort understanding.

7. Longest Substring Without Repeating Characters

Use sliding window technique with a hash set to track characters. Expand the window right and shrink from left when duplicates found. O(n) time complexity. Essential sliding window pattern.

8. Detect Cycle in a Linked List

Use Floyd's Tortoise and Hare algorithm with slow and fast pointers. If they meet, a cycle exists. To find the cycle start, reset one pointer to head and move both at same speed. O(n) time, O(1) space.

9. Rotate Array by K Positions

Rotate array right by k steps using the reverse technique. Reverse entire array, then reverse first k elements, then reverse remaining. O(n) time, O(1) space. Tests array manipulation skills.

10. String Anagram Check

Check if two strings are anagrams by comparing character frequency counts. Use a hash map or sort both strings and compare. Hash map approach is O(n) time. Sorting approach is O(n log n). Common string manipulation question.

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Conclusion: Master these fundamental DSA patterns and you will be able to solve 80 percent of coding interview problems. Practice daily on LeetCode, focus on understanding patterns rather than memorizing solutions.

Tags: #DSA #CodingInterview #Arrays #LinkedList #Strings #LeetCode #MAANG #DataStructures #Algorithms #CodingPrep2026