GoFishProblem.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GoFishProblem
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Random random = new Random();

            int inputNumPlayers = 12;
            int inputNumSimulations = 10000000;
            int resultingNumSimulationsWhereNoPairs = 0;

            for (int eachSimulation = 0; eachSimulation < inputNumSimulations; eachSimulation++)
            {
                // Construct random deck:

                List<int> originalDeck = new List<int>();
                List<int> randomDeck = new List<int>();

                for (int i = 0; i < 48; i++)
                {
                    originalDeck.Add(i / 2);
                }

                while (originalDeck.Count > 0)
                {
                    // Pick random card from originalDeck, move to randomDeck:
                    int randomSlotFromOriginalDeck = random.Next(0, originalDeck.Count);
                    randomDeck.Add(originalDeck[randomSlotFromOriginalDeck]);
                    originalDeck.RemoveAt(randomSlotFromOriginalDeck);
                }

                // Deal to players, as soon as a player gets the same card twice, stop:

                List<List<int>> playersHands = new List<List<int>>();
                bool atLeastOnePair = false;

                for (int eachPlayer = 0; eachPlayer < inputNumPlayers; eachPlayer++)
                {
                    var thisPlayersHand = new List<int>();
                    playersHands.Add(thisPlayersHand);

                    //Console.WriteLine();

                    for (int eachHandSlot = 0; eachHandSlot < 4; eachHandSlot++)
                    {
                        // Pick random card from randomDeck:
                        int randomSlotFromDeck = random.Next(0, randomDeck.Count);
                        int chosenCardValue = randomDeck[randomSlotFromDeck];

                        //Console.WriteLine(chosenCardValue);

                        // Does this player have this card value already? If so, we're done.
                        if (thisPlayersHand.Contains(chosenCardValue))
                        {
                            atLeastOnePair = true;
                            break;
                        }

                        // Otherwise move the card from deck to this players hand:
                        thisPlayersHand.Add(chosenCardValue);
                        randomDeck.RemoveAt(randomSlotFromDeck);
                    }

                    if (atLeastOnePair)
                        break;
                }

                if (!atLeastOnePair)
                {
                    //Console.WriteLine("NO PAIRS");
                    resultingNumSimulationsWhereNoPairs++;
                }
                else
                {
                    //Console.WriteLine("PAIR OCCURRED");
                }

                //Console.ReadLine();
            }

            Console.WriteLine((100 * resultingNumSimulationsWhereNoPairs / (double)inputNumSimulations) + "% chance of nobody having any pair");
        }
    }
}