8.9.9

using System;
public class texto
{
    public string let;
    public int nlet;
    public int sh;
    public texto(string a, int b, int c)
    {
        let = a;
        nlet = b;
        sh = c;
    }
}
class Test
{
    public static void Main()
    {
        Console.WriteLine("Введите текст");
        string c = Console.ReadLine();
        int g = c.Length;
        for (int i = 0; i < c.Length; i++)
        {
            if (c[i] == ' '||c[i]==','||c[i]=='.')
            {
                g--;
            }
        }
        string v = c;
        c = v.ToLower();
        Console.WriteLine("В тексте {0} букв", g);
        texto[] m = new texto[g-1];
        int y = 0;
        int prov = 0;
        double s = 0;
        for (int i = 1; i <c.Length; i++)
        {
            prov = 0;
            if (c[i] != ' ' && c[i] != ',' && c[i] != '.'&& c[i-1] != ' ' && c[i-1] != ',' && c[i-1] != '.')
            {
                if (y > 0)
                {
                    for (int t = 0; t <= y - 1; t++)
                    {
                        if (String.Concat(c[i - 1], c[i]) == m[t].let)
                        {
                            m[t].nlet++;
                            prov++;
                            s++;
                        }
                    }
                }
                if (prov == 0)
                {
                    int f = 0;
                    int a = 3;
                    m[y] = new texto(String.Concat(c[i - 1], c[i]), 1, y);
                    while (f < c.Length)
                    {
                        if (c[f] == m[y].sh)
                        {
                            f = 0;
                            m[y].sh = y + a;
                            a++;
                        }
                        f++;
                    }
                    if (i < c.Length - 1)
                    {
                        y++;
                    }
                    s++;
                }
            }
        }
        s = s / y;
        string v = c;
        Console.WriteLine();
        Console.WriteLine("Шифры");
        Console.WriteLine();
        int r = 0;
        for (int i = 0; i < y; i++)
        {
            if (m[i].nlet > s)
            {
                if (r % 2 == 0)
                {
                    v = c.Replace(m[i].let, m[i].sh.ToString());
                    Console.WriteLine("Шифр {0} -> '{1}'", m[i].sh, m[i].let);
                    r++;
                }
                else
                {
                    c = v.Replace(m[i].let, m[i].sh.ToString());
                    Console.WriteLine("Шифр {0} -> '{1}'", m[i].sh, m[i].let);
                    r++;
                }
            }
        }
        if (r > 0)
        {
            Console.WriteLine();
            Console.WriteLine("Итоговый текст");
            if (r % 2 == 0)
            {
                Console.WriteLine(c);
            }
            else
            {
                Console.WriteLine(v);
            }
        }
        else
        {
            Console.WriteLine("Повторяющихся комбинаций нет");
        }

    }
}