using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Return duplicate character count for Better Bigger (only the chars that have frequency > 1)");

        string input = "Better Bigger";

        Dictionary<char, int> dict = CountDuplicateCharacters(input);

        Console.WriteLine("CountDuplicateCharacters1 ==> ");

        foreach(var (key, value) in dict)

        {

            if(value > 1)

            {

                Console.WriteLine("Char:" + key.ToString() + " Value: " + value);           

            }

        }

        Dictionary<char, int> dict2 = CountDuplicateCharacters2(input);

        Console.WriteLine("CountDuplicateCharacters2 ==> ");

        foreach(var (key, value) in dict2)

        {

            if(value > 1)

            {

                Console.WriteLine("Char:" + key.ToString() + " Value: " + value);           

            }

        }

    }

    public static Dictionary<char, int> CountDuplicateCharacters(string input)

    {

        Dictionary<char, int> dict = new Dictionary<char, int>();

        foreach(char c in input)

        {

            if (!dict.ContainsKey(c))

                dict[c] = 0;

​

            dict[c]++;  // Increment directly

        }

        return dict;

    }

    public static Dictionary<char, int> CountDuplicateCharacters2(string input)

    {

        // group by the characters, get character counts > 1, return the char freq mapping

        return input.GroupBy(g => g)

                    .Where(g => g.Count() > 1)

                    .ToDictionary(g => g.Key, g => g.Count());

    }

}