using System;

using System.Collections.Generic;

using System.Linq;

/*https://codereview.stackexchange.com/questions/868/calculating-entropy-of-a-string/926#926*/

public class Program

{

    public static void Main()

    {

        string firstname = "Js";

        int uniqueChars = Entropy(firstname);

        double uniqueLengthRatio = (double)firstname.Length / (double)uniqueChars;

        Console.WriteLine("unique: " + uniqueChars + ", length:"  + firstname.Length +" , ratio: " + uniqueLengthRatio);

    }

    public static int Entropy(string s)

    {

        var hs = new HashSet<char>();

        foreach (char c in s)

            hs.Add(c);

        return hs.Count();

    }

}