DSAlgoPatterns - DSA Pattern-Based Learning Repository

Welcome to DSAlgoPatterns, a structured collection of Data Structures and Algorithms (DSA) problems designed to help you build problem-solving intuition across C++, Python, and Java.

Each topic follows a pattern-based approach, ensuring you recognize and apply solutions effectively. Every problem includes:

• Solutions in C++, Python, and Java
• An explanation (.md file) for clarity
• Key concepts and approaches
• Real-world analogy

This repository is built to be a self-sustained learning resource, whether you're preparing for coding interviews, competitive programming, or improving problem-solving skills.

🟢 Beginner | 🟡 Intermediate | 🔴 Advanced

📂 Repository Blueprint

Arrays & Hashing

• Subarrays/Substrings 🟡
  • Maximum Subarray (Kadane's) 🟢 (Added)
  • Minimum Window Substring 🔴
  • Longest Substring Without Repeating 🟡
• Frequency Counting 🟢
  • Two Sum 🟢
  • Two Sum II (Input Sorted) 🟢
  • Group Anagrams 🟡
  • Top K Frequent Elements 🟡
• Prefix Sum & Hashing 🟡
  • Find Middle Index in Array 🟢
  • Product Except Self 🟡
  • Maximum Product Subarray 🟡
  • Number of Ways to Split Array 🟡
  • Range Sum Query 2D 🟡

Two Pointers

• Collision Pointers 🟡
  • Container with Most Water 🟡
  • Trapping Rain Water 🔴
  • 3Sum 🟡
• Fast & Slow Pointers 🟡
  • Linked List Cycle II 🟡
  • Remove Nth Node from End 🟡
  • Find the Duplicate Number 🟡
  • Palindrome Linked List 🟢
• In-place Reversal 🟡
  • Reverse Linked List 🟢
  • Reverse Nodes in k-Group 🔴
  • Swap Nodes in Pairs 🟡
  • Rotate Array 🟡
• Dutch National Flag 🟡
  • Sort Colors 🟡

Binary Search

• Classic Binary Search 🟢
  • Find Target in Sorted Array 🟢
  • Search Insert Position 🟢
• Rotated Arrays 🟡
  • Find Minimum in Rotated Sorted Array 🟡
  • Search in Rotated Sorted Array 🟡
• Answer Optimization 🟡
  • Capacity to Ship Packages 🟡
  • Koko Eating Bananas 🟡
  • Split Array Largest Sum 🔴
• Advanced 🔴
  • Single Element in Sorted Array 🟡
  • Find in Mountain Array 🔴
  • Median of Two Sorted Arrays 🔴

Sliding Window

• Fixed Size 🟡
  • Maximum Sum Subarray of Size K 🟢
  • Permutation in String 🟡
  • Repeated DNA Sequences 🟡
  • Sliding Subarray Beauty 🟡
• Variable Size 🟡
  • Longest Substring Without Repeating 🟡
  • Minimum Size Subarray Sum 🟡
  • Count Number of Nice Subarrays 🟡
  • Longest Repeating Character Replacement 🟡
• Monotonic Queue/Stack 🔴
  • Sliding Window Maximum 🔴
  • Longest Continuous Subarray (Absolute Diff) 🟡

Backtracking

• Permutations 🟡
  • Permutations I & II 🟡
  • N-Queens 🔴
  • Sudoku Solver 🔴
• Combinations 🟡
  • Combination Sum I & II 🟡
  • Generate Parentheses 🟡
• Subsets 🟡
  • Subsets I & II 🟡
  • Palindrome Partitioning 🟡
  • Word Search 🟡

Graphs

• BFS 🟡
  • Shortest Path in Binary Matrix 🟡
  • Rotten Oranges 🟡
  • As Far From Land as Possible 🟡
  • Word Ladder 🔴
• DFS 🟡
  • Number of Islands 🟡
  • Number of Closed Islands 🟡
  • Coloring a Border 🟡
  • Number of Enclaves 🟡
  • Time Needed to Inform All Employees 🟡
• Advanced Algorithms 🔴
  • Dijkstra's Shortest Path 🔴
  • Topological Sort 🔴
  • Kruskal's (Union-Find) 🔴
• Union-Find 🟡
  • Redundant Connection 🟡
  • Number of Provinces 🟡
  • Accounts Merge 🟡

1-D DP

• Knapsack Variants 🟡
  • Subset Sum 🟡
  • Coin Change 🟡
  • Target Sum 🟡
  • Partition Equal Subset Sum 🟡
  • Ones and Zeroes 🟡
• Longest Increasing Subsequence (LIS) 🟡
  • Standard LIS 🟡
  • Russian Doll Envelopes 🔴
• House Robber Series 🟡
  • House Robber I & II 🟡
  • Last Stone Weight II 🟡

2-D DP

• Grid Problems 🟡
  • Unique Paths 🟡
  • Minimum Path Sum 🟡
  • Dungeon Game 🔴
• String DP 🟡
  • Longest Common Subsequence 🟡
  • Edit Distance 🟡
  • Interleaving String 🟡
• Matrix Chain 🔴
  • Burst Balloons 🔴
  • Minimum Cost Tree from Leaf Value 🔴

Bit Manipulation

• XOR Tricks 🟡
  • Single Number I/II/III 🟡
  • Find Original Array of Prefix XOR 🟡
  • XOR Queries of a Subarray 🟡
• Bitmasking 🟡
  • Subset Generation 🟡
  • N-Queens (Bitmask) 🔴
  • Maximum Product of Word Lengths 🟡
• Arithmetic 🟢
  • Add Without Arithmetic Operators 🟡
  • Power of Two 🟢
  • Reverse Bits 🟢

Math & Geometry

• Number Theory 🟡
  • GCD & LCM 🟢
  • Prime Checks 🟡
  • Perfect Squares 🟡
• Coordinate Geometry 🟡
  • Overlapping Rectangles 🟡
  • Convex Hull 🔴
  • K Closest Points to Origin 🟡
• Matrix Operations 🟡
  • Rotate Image 🟡
  • Spiral Matrix 🟡
  • Set Matrix Zeroes 🟡
  • Game of Life 🟡

Heap, Merge, & Stacks

• Top K & K-way Merge 🟡
  • Top K Frequent Elements 🟡
  • Kth Largest Element 🟡
  • Ugly Number II 🟡
  • Merge K Sorted Lists 🔴
• Monotonic Stack 🟡
  • Daily Temperatures 🟡
  • Next Greater Element II 🟡
  • Next Greater Node in Linked List 🟡
  • Online Stock Span 🟡
  • Maximum Width Ramp 🟡
  • Largest Rectangle in Histogram 🔴
• Two Heaps 🔴
  • Find Median from Data Stream 🔴
  • Sliding Window Median 🔴
  • IPO 🔴

Trees & Trie

• Tree Traversals 🟡
  • Level Order Traversal 🟢
  • Zigzag Level Order 🟡
  • Even Odd Tree 🟡
  • Deepest Leaves Sum 🟡
• Tree Construction 🟡
  • Construct BT from Preorder/Inorder 🟡
  • Construct BST from Preorder 🟡
  • Maximum Binary Tree 🟡
• Advanced Tree Problems 🔴
  • All Nodes Distance K 🟡
  • Add One Row to Tree 🟡
  • Maximum Width of Binary Tree 🟡
  • Validate BST 🟡
• Trie 🟡
  • Implement Trie 🟡
  • Word Search II 🔴
  • Design Add & Search Words 🟡

Greedy & Design

• Greedy 🟡
  • Jump Game II 🟡
  • Gas Station 🟡
  • Bag of Tokens 🟡
  • Boats to Save People 🟡
  • Wiggle Subsequence 🟡
  • Candy 🔴
• Design Data Structures 🟡
  • LRU Cache 🟡
  • LFU Cache 🔴
  • Design Twitter 🟡
  • Design Browser History 🟡
  • Design Circular Deque 🟡
  • Snapshot Array 🟡

• Each topic folder contains problems implemented in three languages.
• Every problem has an accompanying .md file explaining approaches, time complexity, and best pr actices.

🛠 How to Use This Repository

1. Pick a pattern-based topic from the Topics Covered section.
2. Read the theory (if available) before solving problems.
3. Solve problems in your preferred language (C++, Python, Java).
4. Refer to the explanation (.md file) if needed.
5. Compare implementations across languages to recognize common patterns.
6. Revisit problems periodically for retention.

(⚡ More topics will be added as we progress!)

📑 Language-Specific Notes

Language	Key Considerations
C++	STL (vector, set, unordered_map, priority_queue) is useful. Efficient memory management is key.
Python	List comprehensions, collections module, and heapq simplify solutions. Python's recursion depth needs handling.
Java	Uses ArrayList, HashMap, and PriorityQueue. Extra attention to handling large numbers and recursion stack size.

Tip: If you're learning all three languages, compare implementations to spot similarities and differences!

📈 Future Scope & Contributions

🔹 Planned Additions:

• 📌 More problems covering all patterns.
• 📌 Code optimizations and best practices.
• 📌 Company-wise problem tagging (Google, Amazon, etc.).
• 📌 Adding video explanations for complex topics.
• 📌 Interactive challenges and quizzes for learning reinforcement.
• 📌 LeetCode, CodeChef, and CodeForces problem mapping.
• 📌 Performance analysis of different approaches.

✨ Keep Learning & Happy Coding!

🔹 This repository is a work in progress and will keep evolving. If it helps you, drop a ⭐ on GitHub!

🚀 Let's crack DSA, one pattern at a time! 🚀