zad 2

  //a
                        int n = 20, k = 0, k2 = 0, a = 0, a2 = 0;
                        Random rand = new Random();
                        int[] tab = new int[21];

                        for (int i = 0; i < n; i++)
                        {
                            tab[i] = rand.Next(10, 21);
                            Console.WriteLine(tab[i]);

                            if (tab[i] % 2 == 0)
                            {
                                a++;
                                k += tab[i];
                            }
                            else
                            {
                                a2++;
                                k2 += tab[i];
                            }
                        }
                        double wynikp = (double)k / (double)a;
                        double wynikn = (double)k2 / (double)a2;

                        double wynik = wynikp - wynikn;
                        Console.WriteLine("Różnica : " + wynik);
                        //b
                        //start sortowania
                        int n1 = 20, tmp = 0;
                        do
                        {
                            for (int i = 0; i < n1 - 1; i++)
                            {
                                if (tab[i] > tab[i + 1])
                                {
                                    tmp = tab[i];
                                    tab[i] = tab[i + 1];
                                    tab[i + 1] = tmp;

                                }

                            }
                            n1--;
                        }while (n1 > 1);

                        //koniec sortowania

                        int z;
                        for ( z = 0; z < 20; z++)
                        {
                            Console.Write(tab[z]+", ");
                        }
                        tab[20] = 1;
                        int l_w = 0, ilosc = 0;
                        for (int c = 0; c < 20; c++)
                        {

                            if (tab[c] == tab[c + 1])
                            {
                                l_w++;
                            }
                            else
                            {
                                    l_w--;
                                    if (l_w % 2 == 0)
                                    {
                                        l_w = 0;
                                        ilosc++;
                                    }
                                    else
                                    {
                                        l_w = 0;
                                    }
                            }
                        }
                        Console.WriteLine("Ilosc liczb (b): " + ilosc);