using System;

using System.Collections.Generic;

​

public class Hobbies

{

    private readonly Dictionary<string, string[]> hobbies = new Dictionary<string, string[]>();

    public void Add(string hobbyist, params string[] hobbies)

    {

        this.hobbies.Add(hobbyist, hobbies);

    }

    public List<string> FindHobbyists(string hobby)

    {

        var hobbyists = new List<string>();

        if (string.IsNullOrEmpty(hobby))

        {

            throw new Exception("Please enter hobby.");

        }

        foreach (KeyValuePair<string, string[]> h in hobbies)

        {

            foreach (string hobb in h.Value)

            {

                if (hobb == hobby)

                {

                    hobbyists.Add(h.Key);

                    break;

                }

            }

        }

        return hobbyists;

    }

    public static void Main(string[] args)

    {

        Hobbies hobbies = new Hobbies();

        hobbies.Add("John", "Piano", "Puzzles", "Yoga");

        hobbies.Add("Adam", "Drama", "Fashion", "Pets");

        hobbies.Add("Mary", "Magic", "Pets", "Reading");

        hobbies.FindHobbyists("Yoga").ForEach(item => Console.WriteLine(item));

    }

}