using System;


namespace Lab1_wariacje_bez_powtorzen
{
    class war_bez_powt
    {
        static void Main()
        {
            int size = 4;
            int length = 2;

            char[] variations = new char[length];
            char[] initailSet = { 'a', 'b', 'c', 'd' };

            GenerateVariationsWithoutRepetitions(0, variations, initailSet, size, length);
            Console.ReadKey();
        }

        static void GenerateVariationsWithoutRepetitions(int index, char[] variations, char[] set, int size, int length)
        {
            if (index >= length)
            {
                PrintVariations(variations);
            }
            else
            {
                for (int i = index; i < size; i++)
                {
                    variations[index] = set[i];
                    Swap(ref set[i], ref set[index]);
                    GenerateVariationsWithoutRepetitions(index + 1, variations, set, size, length);
                    Swap(ref set[i], ref set[index]);
                }
            }
        }

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

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