Online Judge Platform

A comprehensive online judge platform that allows users to solve programming problems in C++, Java, and Python with real-time compilation and execution.

Features

🚀 Core Features

• Multi-language Support: C++, Java, and Python compilation and execution
• Real-time Code Execution: Instant feedback on code compilation and execution
• Problem Management: Browse, filter, and solve programming problems
• Submission Tracking: Track all your submissions with detailed results
• Test Case Validation: Automatic validation against hidden test cases
• User Authentication: Secure user registration and login system

💻 Code Editor Features

• Monaco Editor: Professional code editor with syntax highlighting
• Language Toggle: Easy switching between C++, Java, and Python
• Code Templates: Pre-filled code templates for each language
• Custom Input Testing: Test your code with custom inputs before submission

📊 Problem Features

• Difficulty Levels: Easy, Medium, and Hard problems
• Tag System: Problems categorized by algorithms and data structures
• Detailed Descriptions: Comprehensive problem statements with examples
• Sample I/O: Sample inputs and outputs for better understanding
• Statistics: View acceptance rates and submission counts

🎯 Submission System

• Instant Processing: Fast compilation and execution of code
• Detailed Results: Get comprehensive feedback on your submissions
• Status Tracking: Real-time status updates (Pending, Accepted, Wrong Answer, etc.)
• Execution Metrics: View execution time and memory usage
• Error Messages: Detailed error information for debugging

Technology Stack

Backend

• Node.js with Express.js framework
• MongoDB with Mongoose ODM
• JWT for authentication
• bcryptjs for password hashing
• Child Process for code execution
• File System operations for temporary file management

Frontend

• React 19 with functional components and hooks
• React Router DOM for client-side routing
• Monaco Editor for code editing
• Tailwind CSS for responsive styling
• Axios for API communication
• React Hot Toast for notifications
• Vite for fast development and building

Compiler Support

• C++: GCC with C++17 standard
• Java: JDK 11+ with automatic class detection
• Python: Python 3.x interpreter

Installation and Setup

Prerequisites

• Node.js (v14 or higher)
• MongoDB (local or cloud instance)
• GCC compiler (for C++)
• Java JDK (for Java)
• Python 3.x (for Python)

Backend Setup

1. Navigate to the backend directory:

   cd auth-backend

2. Install dependencies:

   npm install

3. Create a .env file with the following variables:

   MONGO_URI=your_mongodb_connection_string
   JWT_SECRET=your_jwt_secret_key
   PORT=5000
   NODE_ENV=development

4. Seed the database with sample problems:

   node seed.js

5. Start the development server:

   npm run dev

Frontend Setup

1. Navigate to the frontend directory:

   cd auth-frontend

2. Install dependencies:

   npm install

3. Create a .env file:

   VITE_API_URL=http://localhost:5000/api

4. Start the development server:

   npm run dev

API Endpoints

Authentication

• POST /api/users/register - User registration
• POST /api/users/login - User login
• GET /api/users/profile - Get user profile (protected)

Problems

• GET /api/problems - Get all problems with filtering
• GET /api/problems/:id - Get specific problem
• POST /api/problems - Create new problem (admin only)
• PUT /api/problems/:id - Update problem (admin only)
• DELETE /api/problems/:id - Delete problem (admin only)
• GET /api/problems/stats - Get problem statistics

Submissions

• POST /api/submissions - Submit solution
• POST /api/submissions/test - Test code without submission
• GET /api/submissions/:id - Get submission details
• GET /api/submissions/user/:userId - Get user's submissions
• GET /api/submissions/problem/:problemId - Get problem submissions (admin)
• GET /api/submissions/stats - Get submission statistics

Usage Guide

For Students/Programmers

1. Register/Login: Create an account or login to existing account
2. Browse Problems: Navigate to the problems page to see available challenges
3. Filter Problems: Use difficulty and tag filters to find suitable problems
4. Solve Problems: Click on a problem to view details and start coding
5. Choose Language: Select your preferred programming language (C++/Java/Python)
6. Write Code: Use the Monaco editor to write your solution
7. Test Code: Use custom input to test your code before submission
8. Submit Solution: Submit your code for evaluation
9. View Results: Check your submission status and results
10. Track Progress: View all your submissions in the submissions page

For Administrators

1. Login as Admin: Use admin credentials to access admin features
2. Create Problems: Add new programming problems with test cases
3. Manage Problems: Edit or delete existing problems
4. Monitor Submissions: View all submissions for problems
5. Review Statistics: Access platform-wide statistics

Default Admin Account

After running the seed script, you can login as admin using:

• Email: admin@onlinejudge.com
• Password: admin123

Code Execution Security

The platform implements several security measures:

1. Process Isolation: Each code execution runs in a separate process
2. Time Limits: Configurable execution time limits to prevent infinite loops
3. Memory Limits: Memory usage restrictions (future enhancement)
4. Temporary Files: Automatic cleanup of temporary compilation files
5. Input Sanitization: Proper validation of user inputs

Sample Problems

The platform comes with 5 pre-configured problems:

1. Two Sum (Easy) - Hash table problem
2. Reverse Integer (Medium) - Math problem
3. Valid Parentheses (Easy) - Stack problem
4. Longest Common Subsequence (Hard) - Dynamic programming
5. Fibonacci Number (Easy) - Math/DP/Recursion

Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/new-feature)
3. Make your changes
4. Commit your changes (git commit -am 'Add new feature')
5. Push to the branch (git push origin feature/new-feature)
6. Create a Pull Request

Future Enhancements

• Docker containers for safer code execution
• Memory usage monitoring
• Contest system with time-based competitions
• Plagiarism detection
• Discussion forums for problems
• Editorial solutions
• Rating system for users
• More programming languages (C#, Go, Rust)
• Code sharing and collaboration features
• Mobile responsive improvements

License

This project is licensed under the MIT License - see the LICENSE file for details.

Support

For support, email your questions or create an issue in the repository.

Acknowledgments

• MongoDB for the database solution
• Monaco Editor for the code editing experience
• The open-source community for various packages and tools used