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

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

Introduction

Technical interviews are one of the most challenging parts of placement season. Companies like Google, Microsoft, Amazon, Adobe, Atlassian, and many leading startups evaluate candidates through coding interviews to assess their problem-solving ability, programming skills, and understanding of data structures and algorithms.

The good news is that interview patterns are highly consistent. By mastering a carefully selected set of coding problems, you can build the confidence and experience needed to solve unfamiliar questions during real interviews.

In this guide, we've compiled 30 coding interview questions that every Computer Science student should practice in 2026. These questions cover arrays, strings, linked lists, trees, graphs, dynamic programming, greedy algorithms, and more, making this an excellent roadmap for placement preparation.

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📊 Difficulty Comparison Table

Difficulty	Number of Questions	Focus
🟢 Easy	10	Fundamentals & Logic
🟡 Medium	15	Problem Solving
🔴 Hard	5	Advanced DSA

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Why These Questions Matter

Practicing these questions helps you:

• Improve logical thinking

• Strengthen DSA concepts

• Write optimized code

• Prepare for online assessments

• Build confidence for technical interviews

• Perform better in product-based company interviews

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Top 30 Coding Interview Questions

1. Two Sum

Difficulty

🟢 Easy

Concepts

• Arrays

• Hash Map

Asked In

Google, Amazon, Microsoft

What You'll Learn

Finding pairs efficiently using hashing instead of brute force.

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2. Reverse Linked List

Difficulty: 🟢 Easy

Concepts:

• Linked List

• Pointers

Asked In:
Meta, Amazon

Learn:
Pointer manipulation and iterative thinking.

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3. Valid Parentheses

Difficulty: 🟢 Easy

Concepts:

• Stack

Asked In:
Google, Adobe

Learn:
Stack implementation and bracket matching.

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4. Merge Two Sorted Lists

Difficulty: 🟢 Easy

Concepts:

• Linked List

Asked In:
Microsoft

Learn:
Linked list traversal.

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5. Binary Search

Difficulty: 🟢 Easy

Concepts:

• Searching

Asked In:
Almost every company

Learn:
Logarithmic searching.

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6. Maximum Subarray

Difficulty: 🟡 Medium

Concepts:

• Kadane's Algorithm

Asked In:
Amazon

Learn:
Dynamic Programming basics.

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7. Best Time to Buy and Sell Stock

Difficulty: 🟢 Easy

Concepts:

• Arrays

Asked In:
Google

Learn:
One-pass optimization.

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8. Merge Intervals

Difficulty: 🟡 Medium

Concepts:

• Sorting

Asked In:
Facebook

Learn:
Interval merging.

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9. Climbing Stairs

Difficulty: 🟢 Easy

Concepts:

• Dynamic Programming

Asked In:
Microsoft

Learn:
DP fundamentals.

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10. Longest Substring Without Repeating Characters

Difficulty: 🟡 Medium

Concepts:

• Sliding Window

Asked In:
Google

Learn:
Efficient substring problems.

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Questions 11–30 (Summary Table)

#	Problem	Difficulty	Main Topic
11	Product of Array Except Self	🟡	Arrays
12	Group Anagrams	🟡	Hashing
13	Number of Islands	🟡	Graph
14	Rotting Oranges	🟡	BFS
15	Kth Largest Element	🟡	Heap
16	Top K Frequent Elements	🟡	Heap
17	LRU Cache	🔴	Design
18	Coin Change	🟡	DP
19	House Robber	🟡	DP
20	Word Break	🟡	DP
21	Lowest Common Ancestor	🟡	Tree
22	Diameter of Binary Tree	🟡	Tree
23	Course Schedule	🔴	Graph
24	Detect Cycle in Linked List	🟡	Linked List
25	Queue using Stacks	🟢	Stack
26	Trapping Rain Water	🔴	Two Pointer
27	Sliding Window Maximum	🔴	Deque
28	Median of Two Sorted Arrays	🔴	Binary Search
29	Serialize & Deserialize Binary Tree	🔴	Tree
30	N Queens	🔴	Backtracking

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Best Platforms to Practice

Platform	Best For
LeetCode	Interview Questions
HackerRank	Beginners
GeeksforGeeks	Theory + Practice
Codeforces	Competitive Programming
InterviewBit	Placement Preparation

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Interview Preparation Tips

• Solve coding problems every day.

• Focus on understanding patterns instead of memorizing solutions.

• Time yourself while solving problems.

• Review mistakes and optimize your code.

• Practice explaining your approach aloud, as interviewers evaluate communication as well as coding ability.

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Frequently Asked Questions

Which coding platform is best for placements?

LeetCode is one of the most widely used platforms for interview preparation. GeeksforGeeks and HackerRank are also excellent for strengthening concepts and practicing coding problems.

How many coding questions should I solve?

Quality matters more than quantity. Solving around 300–500 well-chosen questions across different topics provides a strong foundation for technical interviews.

Which programming language should I use?

Choose one language and become highly proficient. C++, Java, and Python are all widely accepted in coding interviews.

Do companies ask only DSA?

No. Many companies also evaluate operating systems, databases, computer networks, object-oriented programming, projects, communication skills, and system design (for experienced roles).

How can I improve speed in coding interviews?

Practice consistently, solve timed challenges, learn common problem-solving patterns, and analyze optimized solutions after attempting each problem yourself.

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Final Thoughts

Coding interviews reward consistent practice, not last-minute preparation. By mastering these 30 questions and understanding the underlying concepts, you'll build stronger problem-solving skills and increase your confidence during technical interviews.

Remember that interviews test your thinking process as much as your final answer. Focus on writing clean, efficient code, explaining your approach clearly, and practicing regularly. With persistence and the right preparation strategy, you'll be well-equipped for placement season and software engineering interviews.

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