🧠 DSA Java Notes

Complete Data Structures & Algorithms guide in Java — with strategies, not just code.

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⚠️ Prerequisites — Start Here First

This repo assumes you already know Java basics.
If you're starting from zero, complete this repo first:

👉 Java Zero to Hero
(Variables, OOP, arrays, methods, loops — everything you need before DSA)

Once you're comfortable with Java, come back here. ✅

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🎯 What Makes This Repo Different

Most DSA repos just show you what the code is.
This repo teaches you how to think — the strategies, patterns, and approaches
that actually help you solve problems in Java.

Every topic includes:

• ✅ Clean, heavily commented Java code
• ✅ Strategy files explaining when and why to use each technique
• ✅ Complexity analysis (time + space)
• ✅ A README in every folder explaining what you'll learn

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🗺️ The Full Learning Path

Step 1 → java-zero-to-hero        ← Java basics (do this first)
Step 2 → DSA-Java-Notes           ← You are here ✅
Step 3 → Java-LeetCode-Solutions  ← Coming soon

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📂 Topics Covered (follow this order)

#	Folder	What You'll Learn
00	Prerequisites & Setup	How to use this repo, BigO intro
01	Arrays & Strings	Two pointer, sliding window, prefix sum
02	Linked Lists	Singly, doubly, fast/slow pointer
03	Stacks & Queues	Stack, Queue, Deque, monotonic stack
04	Recursion & Backtracking	Recursion thinking, backtracking template
05	Searching	Linear, binary search, binary search on answer
06	Sorting	Bubble to quicksort + Java's built-in sort
07	Trees	BFS, DFS, BST, Heap, PriorityQueue
08	Graphs	BFS, DFS, Dijkstra, Topological Sort, Union Find
09	Hashing	HashMap, HashSet, frequency map strategy
10	Dynamic Programming	Memoization, tabulation, knapsack, LCS
11	Greedy	When to use greedy vs DP
12	Java DSA Toolkit	Cheatsheets for collections, patterns, complexity

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🚀 How To Run Any File

javac FileName.java
java FileName

Or open in IntelliJ IDEA / VS Code with Java extension.

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📖 How To Use This Repo

1. Follow the numbered folders in order (00 → 01 → 02 → ...)
2. Read the README.md in each folder first
3. Open the .java files — all notes are in comment form
4. Uncomment and run the code to see it in action
5. Modify the code and experiment — that's how you actually learn

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👤 About Me

Piyush Kumar
📍 CSE – Data Science Student | 🇮🇳 India
Building this for anyone who wants to learn DSA in Java the right way.

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⭐ If this helped you, give it a star — it helps others find it too!