using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var tests = new string[] { "Yellow", "Money", "Purple", "Me", "You", "Hiiiiiiiii" };

        foreach (var t in tests)

            Console.WriteLine("LINQ: " + UniqueStringLinq(t) + ", Non-LINQ: " + UniqueStringNoLinq(t));

    }

    public static string UniqueStringLinq(string str)

    {

        if (str.Length < 3) return str;

​

        var midStr = str.Substring(1, str.Length - 2);

        var midCount = midStr.Distinct().Count();

        return string.Concat(str[0], midCount, str[str.Length - 1]);

    }

    public static string UniqueStringNoLinq(string str)

    {

        if (str.Length < 3) return str;

        var uniqueLetters = new Dictionary<char, int>();

        var midStr = str.Substring(1, str.Length - 2);

        foreach (var c in midStr)

        {

            if (!uniqueLetters.ContainsKey(c))

            {

                uniqueLetters.Add(c, 0);

            }

        }

        var midCount = uniqueLetters.Keys.Count();

        return string.Concat(str[0], midCount, str[str.Length - 1]);

    }

}