Election Voting System

A Java implementation of three different election algorithms: Plurality, Runoff (instant-runoff voting), and Tideman (ranked pairs / Condorcet method).

Overview

This project demonstrates object-oriented design by implementing three distinct voting methods in a clean, modular architecture.

Algorithms

Plurality Election

• Single-choice voting system
• Winner: candidate with most votes
• Time: O(n), Space: O(m)

Runoff Election

• Ranked-choice voting with elimination rounds
• Winner: first candidate with >50% of votes
• Time: O(n·m²), Space: O(n·m)

Tideman Election

• Ranked pairs method with pairwise comparisons
• Uses DFS cycle detection to build preference graph
• Determines Condorcet winner if exists
• Time: O(m² + p·m²), Space: O(m² + p)

Project Structure

src/election/
├── Main.java              # Entry point
├── algorithm/
│   ├── Plurality.java
│   ├── Runoff.java
│   └── Tideman.java
└── util/
    ├── InputUtil.java     # Ballot collection & validation
    └── OutputUtil.java    # Formatting
bin/                       # Compiled classes

Build & Run

Compile:

mkdir -p bin && find src -name "*.java" -print0 | xargs -0 javac -d bin

Run:

java -cp bin election.Main

VS Code: Press F5

Usage

1. Select election method (1-3)
2. Enter candidate names (space-separated)
3. Cast ballots:
   • Plurality: single ID per vote
   • Runoff/Tideman: space-separated IDs in preference order (e.g., 0 1 2)
4. View results and algorithm details

Design Highlights

• OOP: Inner classes (Candidate, Pair), proper encapsulation
• Data Structures: ArrayList, HashMap, 2D arrays for matrices
• Features: Input validation, duplicate detection, user feedback, cycle detection
• Complexity: Analyzed and optimized for each algorithm

Improvements Over CS50

• Converted from procedural C to OOP Java
• Dynamic collections instead of fixed arrays
• Enhanced validation and error handling
• Better user experience with formatted output
• Graph algorithms (DFS) for cycle detection