Top 30 Coding Interview Questions Every Computer Science Student Should Practice (2026)

Top 30 Coding Interview Questions Every Computer Science Student Should Practice (2026) 

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Landing a software engineering job in 2026 requires more than just knowing a programming language. Companies like Google, Microsoft, Amazon, Adobe, Atlassian, Flipkart, TCS, Infosys, Accenture, and many startups evaluate candidates based on their problem-solving skills, coding efficiency, and understanding of Data Structures & Algorithms (DSA).

Coding interviews are designed to assess your logical thinking, optimization techniques, and ability to write clean code under time constraints. While the number of possible interview questions is enormous, many companies repeatedly ask similar problem patterns involving arrays, strings, linked lists, trees, graphs, and dynamic programming.

In this guide, we've compiled 30 essential coding interview questions that every Computer Science student should practice before placements or technical interviews. Along with each question, you'll find the difficulty level, key concept, commonly asked companies, and why it's important. Whether you're preparing for campus placements or dream companies, mastering these problems will significantly improve your confidence and interview performance.

"If you prefer learning offline, check out our Recommend Reference Books on Amazon."

Quick Overview Table

TopicQuestions
Arrays1–5
Strings6–10
Linked Lists11–15
Trees16–20
Graphs21–25
Dynamic Programming26–30

⭐ Arrays (Questions 1–5)

1. Two Sum

Difficulty: Easy

Asked By: Google, Amazon, Microsoft

Concept: Hash Map

Why Practice?

One of the most common interview questions used to test your understanding of hashing and time optimization.

2. Best Time to Buy and Sell Stock

Difficulty: Easy

Concept: Greedy

Asked by:
Amazon
Adobe
Microsoft

3. Maximum Subarray

Difficulty: Medium

Concept: Kadane's Algorithm

Asked by:
Google
Meta

4. Merge Intervals

Difficulty: Medium

Concept:
Sorting

5. Rotate Array

Difficulty: Easy

Concept:
Array Manipulation

⭐ Strings (Questions 6–10)

  1. Valid Parentheses

Concept:
Stack

  1. Longest Substring Without Repeating Characters

Concept:
Sliding Window

  1. Group Anagrams

Concept:
Hashing

  1. Longest Palindromic Substring

Concept:
Two Pointers

  1. Reverse Words in a String

Concept:
String Manipulation

⭐ Linked Lists (Questions 11–15)

  1. Reverse Linked List

Concept:
Pointers

  1. Detect Cycle

Concept:
Fast & Slow Pointer

  1. Merge Two Sorted Lists

Concept:
Linked List

  1. Remove Nth Node

Concept:
Two Pointer

  1. Middle of Linked List

Concept:
Fast & Slow Pointer

⭐ Trees (Questions 16–20)

  1. Binary Tree Inorder Traversal
  2. Maximum Depth of Binary Tree
  3. Diameter of Binary Tree
  4. Lowest Common Ancestor
  5. Balanced Binary Tree

⭐ Graphs (Questions 21–25)

  1. BFS Traversal
  2. DFS Traversal
  3. Number of Islands
  4. Clone Graph
  5. Topological Sort

⭐ Dynamic Programming (Questions 26–30)

  1. Climbing Stairs
  2. House Robber
  3. Coin Change
  4. Longest Increasing Subsequence
  5. 0/1 Knapsack

📊 Difficulty Distribution

DifficultyQuestions
Easy12
Medium14
Hard4

📅 30-Day Coding Interview Plan

WeekTopics
Week 1Arrays + Strings
Week 2Linked Lists + Trees
Week 3Graphs
Week 4Dynamic Programming + Revision

Interview Preparation Tips

  • Solve at least 2 problems every day.
  • Don't memorize solutions—understand the underlying pattern.
  • Time yourself while solving.
  • After solving, explain your approach aloud as if you're in an interview.
  • Revise difficult questions every weekend.

Common Mistakes to Avoid

❌ Memorizing code without understanding

❌ Ignoring time complexity

❌ Not practicing edge cases

❌ Switching programming languages too often

❌ Skipping revision

Frequently Asked Questions

Which coding platform is best?

LeetCode is excellent for interview preparation, while HackerRank and GeeksforGeeks are great for beginners and structured practice.

How many coding questions should I solve?

Aiming for 300–500 well-understood problems across different topics is a solid goal for most placement interviews.

Which programming language should I use?

Stick to one language—such as C++, Java, or Python—and become comfortable solving problems in it before learning others.

Is DSA enough for placements?

No. Along with DSA, strengthen your core CS subjects, build projects, prepare your resume, and practice communication skills.

Related Articles

Link these articles you've already published:

  • Complete C Roadmap for Placement Preparation (2026)
  • Top 15 Best Websites to Learn DSA for Free in 2026
  • Top 20 Websites to Practice Coding for Free in 2026
  • Top 20 FREE Coding Resources Every Programmer Should Know in 2026
  • Top 25 VS Code Extensions Every Programmer Should Install (2026)
  • Top 15 GitHub Projects Every Computer Science Student Should Build (2026)

Conclusion

Coding interviews aren't about solving every problem on the internet—they're about recognizing common patterns and applying them confidently. By consistently practicing these 30 essential questions, understanding the underlying concepts, and reviewing your mistakes, you'll be much better prepared for campus placements and software engineering interviews in 2026.


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