PlayDice

output.txt

N=1000 : p=0.16750418760469
N=10000 : p=0.167664269067619
N=100000 : p=0.166234180739775
N=1000000 : p=0.166660555779621
N=10000000 : p=0.166789565558048
Press any key to continue . . .

Program.cs

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

namespace test
{
	class Program
	{
		static int seed;
		
		public static void Main(string[] args)
		{
			seed = Environment.TickCount;
			
			var NList = new List<int>(){ 1000,10000,100000,1000000,10000000};
			NList.ForEach( N => {
			                 var p = PlayDice(N);
			                 Console.WriteLine(String.Format("N={0} : p={1}", N, p.ToString()));
			              });
						
			Console.Write("Press any key to continue . . . ");
			Console.ReadKey(true);
		}
		
		static double PlayDice(int N)
		{
			var students = Enumerable.Range(0, N);
			var sum = students.AsParallel().Sum(_ => GetNumberOfTrial());
			return (double)N / sum;
		}
		
		static int GetNumberOfTrial() {
			var numOfTrial = 0;
			var rnd = new Random(seed++);
			for (; ;){
				var x = rnd.Next(6);
				numOfTrial++;
				if(x == 0) break;
			}
			return numOfTrial;
		}
	}
}