using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("aaabccccdd" +"  - " +Compression1("aaabccccdd"));

        Console.WriteLine("yyyyyzzzzzzzzzz" +"  - "+Compression1("yyyyyzzzzzzzzzz"));

        Console.WriteLine("abcd" +"  - "+ Compression1("abcd"));

        Console.WriteLine("hhhccchhhccc" +"  - "+Compression1("hhhccchhhccc"));

        Console.WriteLine( ""+ "  - "+Compression1(""));

        Console.WriteLine("a" +"  - "+Compression1("a"));  

        Console.WriteLine("AAAaaabbbBBB" +"  - "+ Compression1("AAAaaabbbBBB"));

        Console.WriteLine("AAAaaabbbBBB" +"  - "+ Compression1("AAAaaabbbBBB",false));

        Console.WriteLine();

        Console.WriteLine("Method 2");

        Console.WriteLine();

        Console.WriteLine("aaabccccdd" +"  - " +Compression2("aaabccccdd"));

        Console.WriteLine("yyyyyzzzzzzzzzz" +"  - "+Compression2("yyyyyzzzzzzzzzz"));

        Console.WriteLine("abcd" +"  - "+ Compression2("abcd"));

        Console.WriteLine("hhhccchhhccc" +"  - "+Compression2("hhhccchhhccc"));

        Console.WriteLine( ""+ "  - "+Compression2(""));

        Console.WriteLine("a" +"  - "+Compression2("a")); 

        Console.WriteLine("AAAaaabbbBBB" +"  - "+ Compression2("AAAaaabbbBBB"));

        Console.WriteLine("AAAaaabbbBBB" +"  - "+ Compression2("AAAaaabbbBBB",false));

    }

    public static string Compression1(string inputStr,bool isCaseAllowed = true)

    {

         try

            {

                string preChara = "";

​

                if (!isCaseAllowed)

                    inputStr = inputStr.ToLower();

​

                return Regex.Replace(inputStr, @"(.)\1*", k => k.Groups[1].Value +

                      (k.Value.Length == 1 ? preChara : k.Value.Length.ToString()));

            }

            catch (Exception ex)

            {

                throw ex;

            }

    }

      public static string Compression2(string a, bool isCaseAllowed = true)

        {

            try

            {

                if (a == string.Empty)

                     return "";

                if (!isCaseAllowed)

                    a = a.ToLower();

​

                int n = a.Length;

                var m = string.Empty;

                if (n == 1)

                     return a[0].ToString();

                for (int i = 0; i < n; i++)

                {

                    int count = 1;

                    while (i < n - 1 && a[i] == a[i + 1])

                    {

                        count++;

                        i++;

                    }

​

                    if (count == 1)

                    {

                        m = m + a[i];

​

                    }

                    else

                    {

                        m = m + a[i] + count.ToString();

                    }

                }

​

                return m;

            }

            catch (Exception ex)

            {

​

                throw ex;

            }

        }

}