📌 Introduction
Every year, thousands of students prepare for coding interviews and placements. While there are thousands of problems online, the truth is:
👉 A handful of DSA problems keep getting repeated across companies like TCS, Infosys, Wipro, Amazon, Microsoft, and Google.
If you master these repeated interview problems, you cover 60–70% of coding test patterns.
🧩 Most Repeated DSA Problems
Here’s a curated list of frequently asked DSA problems, categorized by topic.
🔢 Arrays
Two Sum Problem (Find indices of two numbers that add up to a target).
Kadane’s Algorithm (Maximum subarray sum).
Rotate Array (Left/Right rotation).
Find Missing Number in an array from 1 to n.
Majority Element (appearing more than n/2 times).
💡 Common in Infosys, TCS, Accenture, Wipro interviews.
🔡 Strings
Check Palindrome String.
Anagram Check (two strings contain same characters).
Longest Common Prefix among given strings.
Valid Parentheses (balanced brackets).
Substring Search (implement strstr/IndexOf).
💡 Frequent in service-based companies and entry-level rounds.
🔗 Linked List
Reverse a Linked List (Iterative + Recursive).
Detect a Cycle (Floyd’s Cycle Detection).
Merge Two Sorted Linked Lists.
Find Middle Element of Linked List.
Remove Nth Node from End.
💡 Infosys, Tech Mahindra, and Amazon often ask these.
📚 Stack & Queue
Implement Stack/Queue using arrays or linked list.
Next Greater Element.
Evaluate Postfix/Prefix Expression.
LRU Cache Implementation.
Sliding Window Maximum.
💡 Popular in Flipkart, Amazon, and Microsoft interviews.
🌳 Trees
Binary Tree Traversals (Inorder, Preorder, Postorder).
Height of a Tree.
Lowest Common Ancestor (LCA).
Diameter of a Tree.
Check if a Tree is Balanced.
💡 Asked in Amazon, Adobe, and Microsoft interviews.
🌐 Graphs
BFS & DFS Traversals.
Detect Cycle in Graph.
Shortest Path (Dijkstra’s Algorithm).
Minimum Spanning Tree (Prim/Kruskal).
Topological Sorting.
💡 Google, Microsoft, and Amazon love graph problems.
🧮 Dynamic Programming (DP)
Fibonacci Series (Memoization + Tabulation).
Longest Common Subsequence (LCS).
Longest Increasing Subsequence (LIS).
0/1 Knapsack Problem.
Coin Change Problem.
💡 DP separates average coders from top-tier candidates in FAANG-level interviews.
📊 Company-Wise Problem Focus
| Company Type | Frequently Asked Problems | Difficulty |
|---|
| Service-based (TCS, Infosys, Wipro, Cognizant) | Arrays (Kadane, Missing Number), Strings (Palindrome, Anagram), Linked List Basics | Easy – Medium |
| Mid-tier (Capgemini, Tech Mahindra, Accenture) | Arrays + Hashing, Linked Lists, Stacks & Queues | Medium |
| Product-based (Amazon, Microsoft, Google, Adobe, Flipkart) | Trees (LCA, Diameter), Graphs (BFS, Shortest Path), DP (Knapsack, LCS) | Medium – Hard |
✅ Summary
The most repeated DSA problems in interviews are:
Arrays: Kadane’s Algorithm, Two Sum, Missing Number.
Strings: Palindrome, Anagram, Valid Parentheses.
Linked List: Reverse, Detect Cycle, Merge Lists.
Stacks/Queues: Next Greater Element, LRU Cache.
Trees/Graphs: Traversals, LCA, BFS/DFS, Shortest Path.
DP: Fibonacci, LCS, Knapsack.
💡 If you practice 200–250 problems covering these patterns, you’ll be ready for most interview coding rounds.
🔎 FAQ
Q1. How many repeated DSA problems should I focus on before placements?
👉 Around 100–150 core problems are enough.
Q2. Can I crack TCS/Infosys with only arrays and strings?
👉 Yes, for service-based companies, those two topics cover most coding tests.
Q3. Do I need to learn Dynamic Programming for Wipro/Accenture?
👉 Not mandatory. Focus more on Arrays, Strings, Linked Lists.
Q4. Which problems are must-do for Amazon interviews?
👉 LRU Cache, Linked List Cycle Detection, Binary Tree LCA, DP (LCS, Knapsack).
Q5. Where can I find a list of all repeated problems?
👉 GeeksforGeeks “Top 100 DSA Problems” and LeetCode’s “Top Interview Questions” section.