Card Shuffling in C#

Question

I am trying to write a code for a project that lists the contents of a deck of cards, asks how much times the person wants to shuffle the deck, and then shuffles them. It has to use a method to create two random integers using the System.Random class.

These are my classes:

Program.cs:

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Deck mydeck = new Deck();
            foreach (Card c in mydeck.Cards)
            {
                Console.WriteLine(c);
            }
            Console.WriteLine("How Many Times Do You Want To Shuffle?");

        }
    }
}

Deck.cs:

namespace ConsoleApplication1
{
    class Deck
    {    
        Card[] cards = new Card[52];
        string[] numbers = new string[] { "2", "3", "4", "5", "6", "7", "8", "9", "J", "Q", "K" };
        public Deck()
        {
            int i = 0;
            foreach(string s in numbers)
            {
                cards[i] = new Card(Suits.Clubs, s);
                i++;

            }
            foreach (string s in numbers)
            {
                cards[i] = new Card(Suits.Spades, s);
                i++;

            }
            foreach (string s in numbers)
            {
                cards[i] = new Card(Suits.Hearts, s);
                i++;

            }
            foreach (string s in numbers)
            {
                cards[i] = new Card(Suits.Diamonds, s);
                i++;

            }
        }

        public Card[] Cards
        {
            get
            {
                return cards;


            }
        }
    }  
}

Enums.cs:

namespace ConsoleApplication1
{        
    enum Suits 
    {
        Hearts,
        Diamonds,
        Spades,
        Clubs
    }
}

Card.cs:

namespace ConsoleApplication1
{
    class Card
    {
        protected Suits suit;
        protected string cardvalue;
        public Card()
        {
        }
        public Card(Suits suit2, string cardvalue2)
        {
            suit = suit2;
            cardvalue = cardvalue2;
        }
        public override string ToString()
        {
            return string.Format("{0} of {1}", cardvalue, suit);
        }
    }
 }

Please tell me how to make the cards shuffle as much as the person wants and then list the shuffled cards.

Answer 1

The shuffling should work in this manner:

You take two random cards in the deck (the index of the card in the deck is the random numbers) And swap positions of the two cards. For instance take card at index 2 and card at index 9 and have them change place.

And that can be repeated a certain number of times.

The algorithm should look something like this:

int firstNum = rnd.Next(52);
int secondNum = rnd.Next(52);

Card tempCard = MyCards[firstNum];
MyCards[firstNum] = MyCards[secondNum];
MyCards[secondNum] = tempCard;

Answer 2

Your Shuffle might work, but it's not really efficient and not lifelike. You should try this way:

//The shuffle goes like this: you take a portion of the deck, then put them in random places
private void Shuffle()
{
 int length = DeckofCards.Count;
 int level = 20; //number of shuffle iterations

 List<Card> Shuffleing; //the part of the deck were putting back
 Random rnd = new Random();
 int PickedCount, BackPortion; //the last used random number

 for (int _i = 0; _i < level; _i++)
 {
  PickedCount = rnd.Next(10, 30); //number of cards we pick out
  Shuffleing = DeckofCards.GetRange(0, PickedCount);
  DeckofCards.RemoveRange(0, PickedCount);

  while (Shuffleing.Count != 0)
  {
   PickedCount = rnd.Next(10, DeckofCards.Count - 1); //where we place a range of cards
   BackPortion = rnd.Next(1, Shuffleing.Count / 3 + 1); //the number of cards we but back in one step
   DeckofCards.InsertRange(PickedCount, Shuffleing.GetRange(0, BackPortion)); //instering a range of cards
   Shuffleing.RemoveRange(0, BackPortion); //we remove what we just placed back
  }
 }
}

This way you might get a more lifelike shuffle with less iterations

Answer 3

Shuffling a deck of cards is something that seems trivial at first, but usually the algorithm that most people come up with is incorrect.

Jeff Atwood (Coding Horror) wrote a few very good articles on the subject:

http://www.codinghorror.com/blog/archives/001008.html

http://www.codinghorror.com/blog/archives/001015.html

(especially the second one is a must-read)