// @nuget: Combinatorics

using System;

using System.Collections.Generic;

using System.Linq;

using Combinatorics.Collections;

​

class Program

{

    static void Main()

    {

        var teams = new List<string> { "WCC4", "WCC5", "WCC6", "BARROG3", "BARROG4", "BARROG5", "FB3", "NDG2" };

        var rounds = new List<List<Tuple<string, string>>> { new List<Tuple<string, string>>(), new List<Tuple<string, string>>(), new List<Tuple<string, string>>() };

​

        var combinations = new Combinations<string>(teams, 2);

        var games = combinations.Where(game => !game[0].Substring(0, game[0].IndexOfAny("0123456789".ToCharArray())).Equals(game[1].Substring(0, game[1].IndexOfAny("0123456789".ToCharArray())))).ToList();

​

        foreach (var round in rounds)

        {

            foreach (var game in games.ToList())

            {

                if (!round.Any(r => r.Item1.Equals(game[0]) || r.Item1.Equals(game[1]) || r.Item2.Equals(game[0]) || r.Item2.Equals(game[1])))

                {

                    round.Add(new Tuple<string, string>(game[0], game[1]));

                    games.Remove(game);

                }

​

                if (round.Count == 4)

                {

                    break;

                }

            }

        }

​

        for (var i = 0; i < rounds.Count; i++)

        {

            Console.WriteLine($"Round {i + 1}:");

            foreach (var game in rounds[i])

            {

                Console.WriteLine($"Game: {game.Item1} vs {game.Item2}");

            }

            Console.WriteLine();

        }

    }

}

​