Data-Structure-Algorithms-Patterns

A complete collection of essential Data Structures & Algorithms patterns with clean, well-explained code examples to master problem-solving code examples to master problem-solving and crack MAANG interviews. Covers core patterns like Sliding Window,Two Pointers,DP, Graphs and Backtracking with templates,complexity notes and practical interview tips

🚀 Data Structures & Algorithms – Crack MAANG & Top Tech Interviews

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🧭 Table of Contents

1. About the Repository
2. Core Concepts
3. Popular DSA Patterns
4. MAANG-Level Problem Set
5. Company-Wise Patterns
6. Contributing
7. Resources & References
8. Author

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📘 About the Repository

This repository is a comprehensive collection of essential Data Structures & Algorithms (DSA) patterns, designed to help you master problem-solving and crack interviews at MAANG, Swiggy, Zomato, and top startups.

Each pattern comes with:

• 🧩 Code templates in Python, C++, or Java
• 🧠 Explanation of core logic
• ⏱️ Time and Space Complexity
• 🏹 Real-world interview problems

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⚙️ Core Concepts

Before diving into patterns, review these fundamental areas:

• Arrays & Strings
• Recursion & Backtracking
• Linked Lists, Stacks, Queues
• Trees & Graphs
• Dynamic Programming
• Sorting & Searching
• Greedy Algorithms
• Bit Manipulation

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💡 Popular DSA Patterns

Pattern	Description	Example Problems
🪟 Sliding Window	Optimize subarray problems for max/min/sum/k-length	Longest Substring Without Repeating Characters (LeetCode #3), Max Consecutive Ones, Minimum Window Substring
🎯 Two Pointers	Works on sorted data to find pairs, partitions	3Sum, Container With Most Water, Remove Duplicates from Sorted Array
🧮 Binary Search	Efficient searching or optimization	Search Rotated Array, Find Peak Element, Median of Two Sorted Arrays
🧵 Fast & Slow Pointers	Detect loops or middle nodes	Linked List Cycle, Palindrome Linked List
🔁 Dynamic Programming	Break down complex problems into subproblems	Longest Increasing Subsequence, House Robber, Coin Change
🌳 Trees & Graphs (DFS/BFS)	Hierarchical and connected data traversal	Binary Tree Level Order, Clone Graph, Word Ladder
🎲 Backtracking	Generate all combinations or paths	N-Queens, Sudoku Solver, Permutations
🧭 Greedy	Local optimal → global optimal	Jump Game, Interval Scheduling, Huffman Encoding
🧮 Prefix Sum / Kadane’s	Efficient range calculations	Maximum Subarray, Subarray Sum Equals K
🧱 Stack & Monotonic Stack	Useful in range problems	Largest Rectangle in Histogram, Daily Temperatures

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🔥 MAANG-Level Problem Set

🟠 Sliding Window

• Longest Substring Without Repeating Characters – Google, Amazon
  👉 Use hash map to track characters; move window start as duplicates appear.
  ⏱ O(N)
• Minimum Window Substring – Meta, Microsoft
  👉 Maintain counts of target chars and shrink window.
  ⏱ O(N)

🔵 Two Pointers

• Container With Most Water – Amazon, Netflix
  👉 Use pointers at both ends; move smaller height inward.
  ⏱ O(N)
• 3Sum Problem – Google, Meta
  👉 Sort + Two Pointers from both ends to find zero-sum triplets.
  ⏱ O(N²)

🟢 Dynamic Programming

• Coin Change – Amazon, Meta
  👉 Classic DP to find min coins for target sum.
  ⏱ O(N * amount)
• Longest Increasing Subsequence – Google, Netflix
  👉 Use DP with binary search for O(N log N).

🟣 Graphs

• Word Ladder – Google, Swiggy
  👉 BFS transformation sequence between words.
  ⏱ O(N * L²)
• Clone Graph – Meta
  👉 DFS clone with hash map to prevent duplication.

🔴 Backtracking

• N-Queens – Amazon, Zomato
  👉 Recursive placement with column and diagonal checks.
  ⏱ O(N!)
• Permutations – Netflix, Google
  👉 Swap and explore recursively.
  ⏱ O(N!)

⚫ Greedy

• Jump Game – Amazon
  👉 Track maximum reachable index at each step.
  ⏱ O(N)
• Activity Selection – Zomato, Swiggy
  👉 Sort by end times; pick non-overlapping activities.
  ⏱ O(N log N)

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🏢 Company-Wise Patterns

Company	Common Patterns	Example Problems
Amazon	Sliding Window, Greedy, Trees	LRU Cache, Jump Game, Binary Tree Zigzag
Google	Graphs, DP, Backtracking	Word Ladder, N-Queens, LIS
Meta	Two Pointers, Hashing, DP	3Sum, Clone Graph, Coin Change
Netflix	Binary Search, Greedy	Container With Most Water, Meeting Rooms II
Swiggy	Graphs, Greedy, BFS	Minimum Path Delivery, Word Ladder
Zomato	DP, Sorting, Greedy	Restaurant Allocation, Activity Scheduling

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📚 Resources & References

• LeetCode
• GeeksForGeeks
• InterviewBit
• Striver’s SDE Sheet
• NeetCode.io

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🤝 Contributing

Contributions are welcome!

1. Fork this repository
2. Create a new branch (feature/new-pattern)
3. Add explanations or code samples
4. Submit a pull request 🚀

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👨‍💻 Author

Pawan Kumar
📍 Product Manager | Data & DevOps Mentor | AI & Cloud Enthusiast
🔗 LinkedIn
✉️ pawankm7654@gmail.com

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