//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {

         const int k = 4;
    const int n = 16;

    static int[] arr = new int[k];
    static int[] free = Enumerable.Range(1, n).ToArray();

    public static void Main(string[] args)
    {
        GenerateVariationsNoRepetitions(0);
    }

    static void GenerateVariationsNoRepetitions(int index)
    {
        if (index >= k)
        {
            PrintVariations();
        }
        else
        {
            for (int i = index; i < n; i++)
            {
                arr[index] = free[i];
                Swap(ref free[i], ref free[index]);
                GenerateVariationsNoRepetitions(index + 1);
                Swap(ref free[i], ref free[index]);
            }
        }
    }

    private static void Swap<T>(ref T v1, ref T v2)
    {
        T old = v1;
        v1 = v2;
        v2 = old;
    }

    static void PrintVariations()
    {
        Console.WriteLine("(" + string.Join(", ", arr) + ")");
    }
    }
}