⚖️ AlgoJudge — Competitive Programming Judge

A fully offline, Java-based competitive programming judge that simulates a real contest environment. Built as a college mini-project covering all 10 modules of the CS2016 (Object-Oriented & Design Patterns) syllabus.

Submit Java solutions → Auto-compile → Execute against hidden test cases → Live leaderboard

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✨ Features

Feature	Description
🔐 Auth System	Register / Login with MD5-hashed passwords and role-based access (Admin / Contestant)
📝 Problem Viewer	Browse 5 built-in problems with statements, sample I/O, difficulty badges, and scoring
💻 Code Editor	In-app editor with syntax template, submit button, and real-time verdict display
⚡ Concurrent Judging	3-thread ExecutorService pool compiles and runs submissions in parallel via ProcessBuilder
🏆 Live Leaderboard	Auto-updating rankings using PriorityQueue + Observer pattern
🛡️ Sandboxed Execution	Time limits enforced per test case; infinite loops are killed automatically
🗄️ SQLite Database	Persistent storage for users, problems, submissions, and leaderboard entries
📦 Serialization	Binary .ser backup of every submission via ObjectOutputStream

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🏗️ Architecture

src/
├── model/          # Data classes — User, Problem, Submission, TestCase, Verdict, LeaderboardEntry
├── interfaces/     # Evaluatable, Rankable, LeaderboardObserver
├── exception/      # CompilationException, TimeLimitExceededException, RuntimeErrorException, DatabaseException
├── collections/    # Leaderboard (PriorityQueue + HashMap), SubmissionCache (HashMap)
├── fileio/         # ProblemFileLoader, TestCaseLoader, SubmissionSerializer
├── db/             # DatabaseManager (Singleton), UserDAO, SubmissionDAO, ProblemDAO
├── engine/         # CompileRunner, TestCaseRunner, JudgeEngine, SubmissionQueue
├── judge/          # AbstractJudge, StandardJudge, StrictJudge, JudgeFactory
├── service/        # UserService, SubmissionService, ContestService
├── ui/             # MainApp, LoginScreen, RegisterScreen, ContestDashboard, ProblemScreen, LeaderboardScreen, AdminScreen
└── Main.java       # Entry point

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📚 Syllabus Module Coverage

Module	Topic	Implementation
1	OOP Basics	Encapsulation, static members, access modifiers across all model classes
2	Classes & Objects	Constructor overloading, toString() / equals() / hashCode() overrides
3	Interfaces & Abstract	Evaluatable, Rankable interfaces; AbstractJudge with Template Method pattern
4	Exception Handling	4 custom exceptions (checked + unchecked), try-with-resources throughout
5	Collections	PriorityQueue, HashMap, ArrayList, LinkedBlockingQueue, Generics
6	File I/O	BufferedReader (char streams), FileInputStream (byte streams), ObjectOutputStream (serialization)
7	Multithreading	ExecutorService, ProcessBuilder, Future, Producer-Consumer with LinkedBlockingQueue
8	GUI (Swing)	7 screens with JTable, JSplitPane, JList, GridBagLayout, ActionListener
9	Design Patterns	Singleton (DatabaseManager), Factory (JudgeFactory), Observer (LeaderboardObserver)
10	Integration	End-to-end: GUI → Service → Engine → DB, with live leaderboard updates

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🚀 Getting Started

Prerequisites

• Java JDK 8 (java and javac must be accessible)
• No frameworks or build tools needed — uses plain javac / java

Setup

git clone https://github.com/prathamb9/OODP_Mini_Project.git
cd OODP_Mini_Project

Compile

# Windows (CMD)
dir /s /b src\*.java > sources.txt
javac -cp "lib\sqlite-jdbc-3.45.1.0.jar;lib\slf4j-api-2.0.9.jar;lib\slf4j-simple-2.0.9.jar" -d out @sources.txt
del sources.txt

Run

java -cp "out;lib\sqlite-jdbc-3.45.1.0.jar;lib\slf4j-api-2.0.9.jar;lib\slf4j-simple-2.0.9.jar" Main

Default Login

Role	Username	Password
Admin	admin	admin123

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📂 Problems Included

#	Title	Difficulty	Max Score
P1	Hello World	Easy	100
P2	Sum of Two Numbers	Easy	100
P3	Fibonacci Number	Easy	100
P4	Prime Check	Medium	150
P5	Palindrome String	Medium	150

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🛠️ Tech Stack

Component	Technology
Language	Java 8
GUI	Java Swing
Database	SQLite (via JDBC)
Build	Plain javac / java
Concurrency	ExecutorService, ProcessBuilder

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👥 Team Contributions

Member	Part	Scope
Member 1	Foundation Layer	Models, Interfaces, Exceptions, Collections, File I/O, Database (Modules 1–6)
Member 2	Judge Engine	CompileRunner, TestCaseRunner, JudgeEngine, AbstractJudge, Factory Pattern (Modules 3, 7, 9)
Member 3	GUI & Integration	Swing screens, Service layer, Observer pattern, Main entry point (Modules 8–10)

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📄 License

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