Competitive Programming Guide
Basic Placement Preparation for Indian Students
Having been through many coding assessments and interviews, I've noticed some key concepts and problems repeat themselves. Whether you're preparing for university placements or coding interviews at MNCs and startups, this guide covers the most common topics you'll encounter.
Target Companies
Mass Recruitment Companies
Top 10 Must-Know Concepts
1. Recursion
Breaking a problem into smaller sub-problems with base condition. Asked in 80% interviews.
2. Sliding Window
Efficiently solving subarray problems by maintaining a window. Very common in arrays.
3. String Manipulation
Operations like reverse, substring, anagram detection. Basic requirement.
4. BFS (Breadth-First Search)
Layer-wise graph traversal for shortest path problems.
5. DFS (Depth-First Search)
Deep exploration in graphs/trees for connected components.
6. Dynamic Programming (DP)
Optimizing recursive problems by caching results.
7. Greedy Algorithms
Making best local decision at each step.
8. Two Pointer Technique
Working with sorted arrays using two index pointers.
9. Backtracking
Trying solutions recursively, undoing if necessary.
10. Binary Search
Searching in sorted array by dividing search space.
15 Must-Solve LeetCode Problems
| # | Concept | Problem & Link |
|---|---|---|
| 1 | Recursion | Max Depth Binary Tree - Problem 104 |
| 2 | Sliding Window | Longest Substring Without Repeat - Problem 3 |
| 3 | String Manipulation | Longest Palindrome - Problem 5 |
| 4 | BFS | Level Order Traversal - Problem 102 |
| 5 | DFS | Number of Islands - Problem 200 |
| 6 | DP | Maximum Subarray - Problem 53 |
| 7 | Greedy | Jump Game - Problem 55 |
| 8 | Two Pointers | 3 Sum Problem - Problem 15 |
| 9 | Backtracking | Permutations - Problem 46 |
| 10 | Binary Search | Basic Binary Search - Problem 704 |
| 11 | Tree Traversal | Inorder Traversal - Problem 94 |
| 12 | OOP Java | LRU Cache - Problem 146 |
| 13 | SQL | Second Highest Salary - Problem 176 |
| 14 | Stack | Valid Parentheses - Problem 20 |
| 15 | Greedy | Burst Balloons - Problem 452 |
Complete DSA Roadmap
Basic Data Structures
- Arrays
- Strings
- Linked Lists
- Stacks
- Queues
Advanced Data Structures
- Trees
- Binary Trees
- Binary Search Trees
- AVL Trees
- B-Trees
- Graphs
- Adjacency Matrix
- Adjacency List
- DFS & BFS
- Shortest Path (Dijkstra, Bellman-Ford)
- Heaps
- Hash Tables
- Union-Find
- Tries
- Segment Tree
Algorithmic Paradigms
- Brute Force
- Divide and Conquer
- Greedy Algorithms
- Dynamic Programming
- Backtracking
- Sliding Window
- Two Pointer Technique
Problem-Solving Approach
Quick Hints - If you see:
Emergency Tips
- If everything fails → Try HashMap
- Start with → Brute Force approach
- Then optimize → Think of better time complexity
- Draw it out → Visualize the problem on paper
- Test with examples → Walk through your solution
Core Topics by Language
Java
- Multithreading & Concurrency
- Exception Handling
- Collections Framework
- Design Patterns (Singleton, Factory)
- Stream API
- Memory Management
JavaScript
- Closures & Scope
- Promises & Async/Await
- Event Loop
- Array Methods
- Object Prototypes
- ES6+ Features
SQL
- JOIN Operations
- Aggregate Functions
- Subqueries
- Database Design
- Normalization
- Index Optimization
Practice Platforms
Personal Note
Hey there! Just a little something from me to you..
Be regular in your practice - that's the most important thing in our line of work. If I can do LeetCode medium problems today and then take a break from coding for 3-4 months, I won't even be able to handle LeetCode easy problems later.
So, whatever time you can spend on coding, make sure you spend it consistently. Participating in weekly contests on platforms like GeeksforGeeks, LeetCode, CodeChef, or Codeforces will give you a reality check on your speed and efficiency.
All the very best for the upcoming placement season!