Tideman’s Ranked Pairs method (developed by Nicolaus Tideman) is a ranked-choice voting algorithm that selects a single winner by constructing a directed graph of pairwise victories and locking in the strongest preferences while avoiding cycles.

This repository provides an object-oriented, benchmarked, file-driven C++17 implementation, wrapped by a Flask API and a minimal HTML front end. It’s now Dockerized (multi-stage) and EC2-ready with Gunicorn for a production-style run.

Live demo: http://13.200.175.4/

• CSV input with support from thousands up to millions of ballots
• High-resolution benchmarking using <chrono>
• Object-oriented design (TidemanElection, VoteParser, Benchmark)
• Robust error handling (bad input, duplicates, file issues)
• Efficient in practice: millions of ballots with ≤9 candidates in milliseconds
• Web service wrapper: C++ executable exposed via Flask API + HTML
• Containerized: Multi-stage Dockerfile, Gunicorn server, EC2-ready (port 80 → 5000)

Example with 3 candidates (Alice, Bob, Charlie):

VoterID,Alice,Bob,Charlie
1,1,2,3
2,2,1,3
3,1,3,2
... up to N rows

Each row = one voter’s ranked preferences. Header defines candidate names; numbers = rank order (1 = top choice).

Recording Preferences took 32109 µs
Adding Pairs took 0 µs
Locking Pairs took 0 µs
Winner: Charlie
Getting Winner took 999 µs

Handles 1,000,000 votes in milliseconds, showing the practicality of the O(n³) algorithm with small n.

• Build preference matrix from all ballots
• Sort candidate pairs by margin of victory
• Lock edges unless they create a cycle
• Candidate with no incoming edge = winner

In the demo below, the Condorcet winner was Charlie.

g++ -std=c++17 -O2 tideman.cpp -o tideman

./tideman --file=ballots.csv

pip install flask flask-cors
python app.py

Then open index.html (via VS Code Live Server or browser) and upload ballots.

1. Launch EC2 (Ubuntu), open Security Group inbound rules:

   • 22 (SSH)
   • 80 (HTTP)

2. Install Docker + Git:

sudo apt update
sudo apt install -y docker.io git

3. Clone & build:

git clone <your-repo-url>
cd <repo>
sudo docker build -t tideman:latest .

4. Run container:

sudo docker run -d --rm -p 80:5000 --name tideman tideman:latest

5. Test:

   • On EC2: curl http://localhost/healthz
   • From your browser: http://<EC2-Public-IP> (port 80 → 5000)