Why Basic DSA Questions Matter in Interviews
Data Structures and Algorithms (DSA) form the core of technical interviews at top tech companies like Google, Amazon, and Microsoft. Even as a fresher, you’ll be tested on:
✔ Problem-solving approach
✔ Efficiency (Big-O notation)
✔ Implementation of basic data structures
✔ Algorithm design skills
Mastering these fundamentals increases your chances of landing a high-paying software engineering job.
50 Basic DSA Interview Questions & Answers
1. Arrays & Strings (Most Common!)
- How to reverse an array? (Ans: Two-pointer technique)
- Find the missing number in 1 to N array. (Ans: Sum formula or XOR method)
- Check if a string is a palindrome. (Ans: Compare start and end characters)
- Remove duplicates from a sorted array. (Ans: Two-pointer approach)
- Find the largest element in an array. (Ans: Linear search or sorting)
2. Linked Lists
- Reverse a linked list. (Ans: Iterative or recursive method)
- Detect a loop in a linked list. (Ans: Floyd’s Cycle Detection)
- Find the middle of a linked list. (Ans: Fast & slow pointer)
3. Stacks & Queues
- Implement stack using arrays. (Ans: LIFO operations with array)
- Check balanced parentheses. (Ans: Stack-based validation)
4. Trees (Binary Trees & BST)
- Find height of a binary tree. (Ans: Recursive DFS)
- Check if a tree is a BST. (Ans: Inorder traversal should be sorted)
- Level order traversal (BFS). (Ans: Queue-based approach)
5. Sorting & Searching
- Implement Binary Search. (Ans: Divide & conquer on sorted array)
- Difference between QuickSort & MergeSort. (Ans: QuickSort is in-place, MergeSort is stable)
6. Recursion & Dynamic Programming
- Fibonacci series using recursion. (Ans: fib(n) = fib(n-1) + fib(n-2))
- What is memoization? (Ans: Storing results to avoid recomputation)
7. Hashing & Sliding Window
- First non-repeating character in a string. (Ans: Hash map tracking counts)
- Longest substring without repeating characters. (Ans: Sliding window technique)
8. Time & Space Complexity (Big-O)
- Time complexity of Bubble Sort? (Ans: O(n²))
- Difference between O(1) and O(n) space? (Ans: Constant vs linear memory)
- How to Prepare for DSA Interviews?
Practice Daily – Solve 1-2 problems on LeetCode/HackerRank
Understand Patterns – Learn standard approaches (Two Pointers, Sliding Window, etc.)
Mock Interviews – Try Pramp or InterviewBit for real-time practice
Revise Complexity – Always analyze time/space complexity
FAQs (Frequently Asked Questions)
1. Which DSA topics are most important for freshers?
Arrays, Strings, Linked Lists, Binary Trees, and Sorting Algorithms cover 80% of interviews.
2. How many DSA questions should I practice?
Aim for 100+ quality problems covering all patterns.
3. Is DSA required for front-end roles?
Yes! Companies like Meta ask DSA even for front-end positions.
Final Tips to Crack DSA Interviews
✅ Start with easy problems before moving to medium/hard
✅ Focus on problem-solving patterns, not memorization
✅ Time yourself – Many interviews are timed (30-45 mins per question)
✅ Explain your approach – Interviewers value communication
Need a structured plan? Download our free 30-day DSA roadmap! 🚀
Which DSA topic do you find most challenging? Let us know in the comments! #DSA #CodingInterviews