Java Practice Repository

A comprehensive collection of Java programming exercises, algorithm problems, and coding challenges from various sources. This repository serves as a portfolio of problem-solving skills and Java proficiency.

📁 Repository Structure

java-practice/
├── leetcode/
│   ├── easy/
│   ├── medium/
│   ├── hard/
│   └── README.md
├── hackerrank/
│   ├── algorithms/
│   ├── data-structures/
│   └── README.md
├── labs/
│   ├── lab01/
│   ├── lab02/
│   └── README.md
├── codewars/
│   └── README.md
├── project-euler/
│   └── README.md
├── data/
│   ├── csv/
│   ├── txt/
│   └── README.md
├── utils/
│   └── Helper.java
├── .gitignore
└── README.md

Folder Purposes

• leetcode/: LeetCode problems organized by difficulty (easy/medium/hard)
• hackerrank/: HackerRank challenges categorized by topic
• labs/: Academic lab assignments and course exercises
• codewars/: Codewars kata solutions
• project-euler/: Project Euler mathematical problems
• data/: Input data files (CSV, TXT, JSON) used across problems
• utils/: Reusable utility classes and helper functions

🚀 Getting Started

Prerequisites

• Java JDK 11 or higher
• Git installed on your machine
• GitHub account

Initial Setup

1. Create a new repository on GitHub

   • Go to https://github.com/new
   • Name it java-practice (or your preferred name)
   • Choose public or private
   • DO NOT initialize with README (we'll push our own)
   • Click "Create repository"

2. Clone the repository to your local machine

   git clone https://github.com/YOUR_USERNAME/java-practice.git
   cd java-practice

3. Create the folder structure

   mkdir -p leetcode/{easy,medium,hard}
   mkdir -p hackerrank/{algorithms,data-structures}
   mkdir -p labs
   mkdir -p codewars
   mkdir -p project-euler
   mkdir -p data/{csv,txt}
   mkdir -p utils

4. Create a .gitignore file

   cat > .gitignore << 'EOF'
   # Compiled class files
   *.class
   
   # Log files
   *.log
   
   # Package Files
   *.jar
   *.war
   *.nar
   *.ear
   *.zip
   *.tar.gz
   *.rar
   
   # IDE-specific files
   .idea/
   .vscode/
   *.iml
   *.iws
   *.ipr
   .DS_Store
   
   # Eclipse
   .classpath
   .project
   .settings/
   
   # Build directories
   target/
   build/
   out/
   bin/
   
   # Temporary files
   *.swp
   *.swo
   *~
   EOF

5. Create this README file

   • Copy this entire content into README.md

6. Initial commit and push

   git add .
   git commit -m "Initial repository setup with folder structure"
   git push -u origin main

   Note: If your default branch is master instead of main, use master in the command above.

📝 Daily Workflow

Adding a New Solution

1. Navigate to the appropriate folder

   cd leetcode/easy

2. Create your Java file

   • Name format: Problem001_TwoSum.java or TwoSum.java
   • Include problem description in comments at the top

3. Write your solution

   /**
    * Problem: Two Sum
    * Source: LeetCode #1
    * Difficulty: Easy
    * Link: https://leetcode.com/problems/two-sum/
    * 
    * Description:
    * Given an array of integers nums and an integer target,
    * return indices of the two numbers that add up to target.
    */
   public class TwoSum {
       public int[] twoSum(int[] nums, int target) {
           // Your solution here
       }
       
       public static void main(String[] args) {
           // Test cases
       }
   }

4. Test your solution locally

   javac TwoSum.java
   java TwoSum

5. Stage and commit your changes

   git add .
   git commit -m "Add LeetCode #1 - Two Sum solution"

6. Push to GitHub

   git push

Working with Data Files

When a problem requires CSV or other input files:

1. Add the data file to the data folder

   cp ~/Downloads/input.csv data/csv/leetcode_problem123_input.csv

2. Reference it in your Java code

   String filePath = "../../data/csv/leetcode_problem123_input.csv";

3. Commit both the code and data

   git add leetcode/medium/Problem123.java
   git add data/csv/leetcode_problem123_input.csv
   git commit -m "Add LeetCode #123 with CSV input data"
   git push

🔄 Git Commands Reference

Basic Commands

# Check status of your repository
git status

# Add all changes
git add .

# Add specific file
git add path/to/file.java

# Commit with message
git commit -m "Your descriptive message"

# Push to GitHub
git push

# Pull latest changes
git pull

# View commit history
git log --oneline

Branch Management (Optional for Advanced Practice)

# Create and switch to new branch
git checkout -b feature/new-problem

# Switch back to main branch
git checkout main

# Merge branch into main
git merge feature/new-problem

# Delete branch after merge
git branch -d feature/new-problem

📋 Best Practices

Code Organization

1. One problem per file - Keep solutions isolated
2. Descriptive naming - Use clear, meaningful names
3. Include problem metadata - Add source, difficulty, and link in comments
4. Write test cases - Include main() method with test cases
5. Document complexity - Note time and space complexity

Commit Message Conventions

Add [Source] #[Number] - [Problem Name]
Update [Source] #[Number] - [Improvement description]
Fix [Source] #[Number] - [Bug description]
Refactor [Source] #[Number] - [Refactoring description]

Examples:

• Add LeetCode #217 - Contains Duplicate
• Update HackerRank - Improve time complexity for sorting problem
• Fix Lab03 - Correct edge case handling

File Naming Conventions

• LeetCode: LC001_TwoSum.java or TwoSum.java
• HackerRank: HR_SortingAlgorithm.java
• Labs: Lab01_Exercise01.java
• Data files: problem_name_input.csv

🎯 Goals

• ✅ Solve at least 3-5 problems per week
• ✅ Cover all difficulty levels
• ✅ Practice different algorithmic patterns
• ✅ Build a strong portfolio of solutions
• ✅ Regular commits to maintain GitHub streak

📊 Progress Tracking

Create a PROGRESS.md file to track your journey:

# Progress Tracker

## Statistics
- Total Problems Solved: X
- LeetCode: X (Easy: X, Medium: X, Hard: X)
- HackerRank: X
- Labs: X

## Current Focus
- Topic: [e.g., Dynamic Programming]
- Goal: [e.g., Solve 10 DP problems this week]

🤝 Contributing

This is a personal practice repository, but if you'd like to share it:

1. Fork the repository
2. Create your feature branch
3. Commit your changes
4. Push to the branch
5. Open a Pull Request

📄 License

This repository is for educational purposes. Problem descriptions are property of their respective platforms.

🔗 Resources

• LeetCode
• HackerRank
• Codewars
• Project Euler
• Java Documentation

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Happy Coding! 🚀