Top 50 DSA Interview Questions for 2026

Data structures and algorithms (DSA) are the most heavily tested topics in software engineering interviews. Companies like Google, Amazon, and Meta use DSA problems to assess your problem-solving ability, code quality, and understanding of time and space complexity. Unlike system design or behavioral rounds, DSA rounds are pass-or-fail: you either solve the problem or you do not.

The good news is that DSA interviews follow predictable patterns. Over 80% of interview questions are variations of well-known problems. If you master the core patterns — two pointers, sliding window, BFS/DFS, dynamic programming, and binary search — you can solve most interview questions in under 30 minutes.

This list is organized by data structure and algorithm pattern. For each question, we provide the difficulty level, the companies that most frequently ask it, and a direct link to our free learning material. We recommend working through each section in order: start with arrays and strings, then move to linked lists, trees, graphs, and finally dynamic programming.

Step 1: Learn the Fundamentals

Before diving into problem-solving, make sure you have a solid understanding of core data structures: arrays, linked lists, stacks, queues, hash maps, trees, graphs, heaps, and tries. For each data structure, understand the time complexity of basic operations (insert, delete, search, traverse). Our free lessons on Guru Sishya cover each data structure with visual explanations, code examples in Java and Python, and practice quizzes.

Step 2: Master Algorithm Patterns

Most DSA interview questions can be mapped to one of 15 common patterns: two pointers, sliding window, fast and slow pointers, merge intervals, cyclic sort, in-place reversal of linked list, BFS, DFS, two heaps, subsets, modified binary search, bitwise XOR, top K elements, K-way merge, and topological sort. Learning to recognize these patterns is more valuable than memorizing individual solutions.

Step 3: Practice with a System

Random practice is inefficient. Follow the structure in this list: start with Easy problems in each category, then move to Medium, and finally Hard. Aim to solve 2-3 problems per day. For each problem, spend 20 minutes attempting it before looking at hints. After solving, write out the time and space complexity and explain your approach out loud (the Feynman technique). Guru Sishya includes a built-in Feynman practice mode for every topic.

Step 4: Simulate Real Interviews

Once you are comfortable solving Medium problems in 20-25 minutes, start timed practice. Use Guru Sishya's interview mode which simulates real interview conditions with a timer, progressive difficulty (Easy, Medium, Hard), and immediate feedback on your solutions. Focus on thinking out loud, asking clarifying questions, and discussing trade-offs — these soft skills matter as much as getting the right answer.

Step 5: Review and Iterate

Track which problems and patterns give you trouble. Guru Sishya's spaced repetition system automatically creates flashcards for problems you get wrong and schedules reviews at optimal intervals. Focus 70% of your time on weak areas and 30% on maintaining strong areas. Most successful candidates report that 4-6 weeks of focused preparation (2-3 hours per day) is sufficient to pass DSA rounds at top companies.