Having problems understanding how Dictionary is working in this program

[Ch33f]

The Form has 4 classes Card, Deck , Player and Game, game being the class that runs everything

The form has 3 TextBox named textName, textBooks and textProgress , ListBox named listHand, 2 buttons named buttonStart and buttonAsk

 

Card

class Card
    {
        public Values Value { get; set; }
        public Suits Suit {get; set;}

    public Card (Suits suit, Values value)
    {
        this.Suit = suit;
        this.Value = value;
    }
    public string Name
    {
        get { return Value.ToString() + " of " + Suit.ToString(); }
    }
    public override string ToString()
    {
        return Name;
    }
       
            public static string Plural(Values value)
            {
                if (value == Values.Six)
                    return "Sixes";
                else
                    return value.ToString() + "s";
            }
        
    }
  

    enum Suits
    {
        Spades,
        Clubs,
        Hearts,
        Diamonds,
    }
    enum Values
    {
        Ace = 1,
        Two = 2,
        Three = 3,
        Four = 4,
        Five = 5,
        Six = 6,
        Seven = 7,
        Eight = 8,
        Nine = 9,
        Ten = 10,
        Jack = 11,
        Queen = 12,
        King = 13,
    }

 

Deck

 class Deck
    {
        private List<Card> cards;
        private Random random = new Random();

        public Deck()
        {
            cards = new List<Card>();
            for (int suit = 0; suit <= 3; suit++)
                for (int value = 1; value <= 13; value++)
                    cards.Add(new Card((Suits)suit, (Values)value));

        }
        public Deck(IEnumerable<Card> initialCards)
        {
            cards = new List<Card>(initialCards);
        }
        public int Count { get { return cards.Count; } }
        public void Add(Card cardToAdd)
        {
            cards.Add(cardToAdd);
        }

        public Card Deal(int index)
        {
            Card CardToDeal = cards[index];
            cards.RemoveAt(index);
            return CardToDeal;
        }
        public void Shuffle()
        {
            List<Card> NewCards = new List<Card>();
            while(cards.Count > 0)
            {
                int CardToMove = random.Next(cards.Count);
                NewCards.Add(cards[CardToMove]);
                cards.RemoveAt(CardToMove);
            }
            cards = NewCards;
        }
        public IEnumerable<string> GetCardNames()
        {
            string[] CardNames = new string[cards.Count];
            for (int i = 0; i < cards.Count; i++)
                CardNames[i] = cards[i].Name;
            return CardNames;
        }
        public void Sort()
        {
            cards.Sort(new CardComparer_bySuit());
        }
        public Card Peek(int cardNumber)
        {
            return cards[cardNumber];
        }
        public Card Deal()
        {
            return Deal(0);
        }
        public bool ContainsValue(Values value)
        {
            foreach (Card card in cards)
                if (card.Value == value)
                    return true;
            return false;
        }
        public Deck PullOutValues(Values value)
        {
            Deck deckToReturn = new Deck(new Card[] { });
            for (int i = cards.Count - 1; i >= 0; i--)
                if (cards[i].Value == value)
                    deckToReturn.Add(Deal(i));
            return deckToReturn;
        }
        public bool HasBook(Values value)
        {
            int NumberOfCards = 0;
            foreach (Card card in cards)
                if (card.Value == value)
                    NumberOfCards++;
            if (NumberOfCards == 4)
                return true;
            else
                return false;
        }

        public void SortByValue()
        {
            cards.Sort(new CardComparer_byValue());
        }


    }

    class CardComparer_bySuit : IComparer<Card>
    {
        public int Compare(Card x, Card y)
        {
            if (x.Suit > y.Suit)
                return 1;
            if (x.Suit < y.Suit)
                return -1;
            if (x.Value > y.Value)
                return 1;
            if (x.Value < y.Value)
                return -1;
            return 0;
        }
    }


    class CardComparer_byValue : IComparer<Card>
    {
        public int Compare(Card x, Card y)
        {
            if (x.Value < y.Value)
                return -1;
            if (x.Value > y.Value)
                return 1;
            if (x.Suit < y.Suit)
                return -1;
            if (x.Suit > y.Suit)
                return 1;
            return 0;
        }
    }

Player

 class Player
    {
        private string name;
        public string Name { get { return name; } }
        private Random random;
        private Deck cards;
        private TextBox textBoxOnForm;
        public Player(String name, Random random, TextBox textBoxOnForm)
        {
            this.name = name;
            this.random = random;
            this.textBoxOnForm = textBoxOnForm;
            this.cards =new Deck(new Card[]{ });
            textBoxOnForm.Text += name + "has joined the game" + Environment.NewLine; 
        }
        public IEnumerable<Values> PullOutBooks()
        {
            List<Values> books = new List<Values>();
            for (int i = 1; i<= 13; i++)
            {
                Values value = (Values)i;
                int howMany = 0;
                for (int card = 0; card < cards.Count; card++)
                    if (cards.Peek(card).Value == value)
                        howMany++;
                if(howMany == 4)
                {
                    books.Add(value);
                    for (int card = cards.Count - 1; card >= 0; card--)
                        cards.Deal(card);
                }
            }
            return books;
        }

        public Values GetRandomValue()
        {
            Card randomCard = cards.Peek(random.Next(cards.Count));
            return randomCard.Value;
        }

        public Deck DoYouHaveAny(Values value)
        {
            Deck cardsIHave = cards.PullOutValues(value);
            textBoxOnForm.Text += Name + "has" + cardsIHave.Count + "" + Card.Plural(value) + Environment.NewLine;
            return cardsIHave;
        }

        public void AskForACard(List<Player> players, int myIndex,Deck stock)
        {
            Values randomValue = GetRandomValue();
            AskForACard(players, myIndex, stock, randomValue);
        }

        public void AskForACard(List<Player>players, int myIndex, Deck stock, Values value)
        {
            textBoxOnForm.Text += Name + "asks if anyone has a " + value + Environment.NewLine;
            int totalCardsGiven = 0;
            for(int i = 0; i<players.Count; i++)
            {
                if(i != myIndex)
                {
                    Player player = players[i];
                    Deck CardsGiven = player.DoYouHaveAny(value);
                    totalCardsGiven += CardsGiven.Count;
                    while (CardsGiven.Count > 0)
                        cards.Add(CardsGiven.Deal());
                }
            }
            if(totalCardsGiven == 0)
            {
                textBoxOnForm.Text += Name + "must draw from teh stock." + Environment.NewLine;
                cards.Add(stock.Deal());
            }
        }
        public int CardCount { get { return cards.Count; } }
        public void TakeCard(Card card) { cards.Add(card); }
        public IEnumerable<string> GetCardNames() { return cards.GetCardNames(); }
        public Card Peek(int cardNumber) { return cards.Peek(cardNumber); }
        public void SortHand() { cards.SortByValue(); }

    }

Game

 class Game
    {
        private List<Player> players;
        private Dictionary<Values, Player> books;
        private Deck stock;
        private TextBox textBoxOnForm;
        public Game(string playerName, IEnumerable<string> opponentNames, TextBox textBoxOnForm)
        {
            Random random = new Random();
            this.textBoxOnForm = textBoxOnForm;
            players = new List<Player>();
            players.Add(new Player(playerName, random, textBoxOnForm));
            foreach (string player in opponentNames)
                players.Add(new Player(player, random, textBoxOnForm));
            books = new Dictionary<Values, Player>();
            stock = new Deck();
            Deal();
            players[0].SortHand();
        }
        private void Deal()
        {
            stock.Shuffle();
            for (int i = 0; i < 5; i++)
                foreach (Player player in players)
                    player.TakeCard(stock.Deal());
            foreach (Player player in players)
                PullOutBooks(player);
        }
        public bool PlayOneRound(int selectedPlayerCard)
        {
            Values cardToAskFor = players[0].Peek(selectedPlayerCard).Value;
            for(int i = 0; i < players.Count; i++)
            {
                if (i == 0)
                    players[0].AskForACard(players, 0, stock, cardToAskFor);
                else
                    players[i].AskForACard(players, i, stock);
                if (PullOutBooks(players[i]))
                {
                    textBoxOnForm.Text += players[i].Name + "drew a new hand" + Environment.NewLine;
                    int card = 1;
                    while(card <=5 && stock.Count > 0)
                    {
                        players[i].TakeCard(stock.Deal());
                        card++;
                    }
                }
                players[0].SortHand();
                if(stock.Count == 0)
                {
                    textBoxOnForm.Text = "The stock is out of cards.Game over!" + Environment.NewLine;
                    return true;
                }
            }
            return false;
        }

        public bool PullOutBooks(Player player)
        {
            IEnumerable<Values> booksPulled = player.PullOutBooks();
            foreach (Values value in booksPulled)
                books.Add(value, player);
            if (player.CardCount == 0)
                return true;
            return false;
        }

        public string DescribeBooks()
        {
            string whoHasWhichBooks = "";
            foreach (Values value in books.Keys)
                whoHasWhichBooks += books[value].Name + "has a book of" + Card.Plural(value) + Environment.NewLine;
            return whoHasWhichBooks;
        }

        public string GetWinnerName()
        {
            Dictionary<string, int> winners = new Dictionary<string, int>();
            foreach (Values value in books.Keys)
            {
                string name = books[value].Name;
                if (winners.ContainsKey(name))
                    winners[name]++;
                else
                    winners.Add(name, 1);
            }
            int mostBooks = 0;
            foreach (string name in winners.Keys)
                if (winners[name] > mostBooks)
                    mostBooks = winners[name];
            bool tie = false;
            string winnerList ="";
                foreach(string name in winners.Keys)
                if(winners[name]== mostBooks)
                {
                    if(!string.IsNullOrEmpty(winnerList))
                    {
                        winnerList += "and";
                        tie = true;
                    }
                    winnerList += name;
                }
            winnerList += "with" + mostBooks + "books";
            if (tie)
                return "A tie between" + winnerList;
            else
                return winnerList;
        }

        public IEnumerable<string> GetPlayerCardNames()
        {
            return players[0].GetCardNames();
        }

        public string DescribePlayerHands()
        {
            string description = "";
                for (int i= 0; i < players.Count; i++)
            {
                description += players[i].Name + "hase" + players[i].CardCount;
                if (players[i].CardCount == 1)
                    description += "card." + Environment.NewLine;
                else
                    description += "cards." + Environment.NewLine;
            }
            description += "The stock has" + stock.Count + "cards left.";
            return description;
        }
    }

The Program

 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private Game game;

        private void buttonStart_Click(object sender, EventArgs e)
        {
            if (String.IsNullOrEmpty(textName.Text))
            {
                MessageBox.Show("Please enter your name", " Can't start the game yet");
                return;
            }
            game = new Game(textName.Text, new List<string> { "Joe", "Bob" }, textProgress);
            buttonStart.Enabled = false;
            textName.Enabled = false;
            buttonAsk.Enabled = true;
            UpdateForm();
        }

        private void UpdateForm()
        {
            listHand.Items.Clear();
            foreach (String cardName in game.GetPlayerCardNames())
                listHand.Items.Add(cardName);
            textBooks.Text = game.DescribeBooks();
            textProgress.Text += game.DescribePlayerHands();
            textProgress.SelectionStart = textProgress.Text.Length;
            textProgress.ScrollToCaret();
        }

        private void buttonAsk_Click(object sender, EventArgs e)
        {
            textProgress.Text = "";
            if(listHand.SelectedIndex < 0)
            {
                MessageBox.Show("Please select a card");
                return;
            }
            if (game.PlayOneRound(listHand.SelectedIndex))
            {
                textProgress.Text += "The winner is..." + game.GetWinnerName();
                textBooks.Text = game.DescribeBooks();
                buttonAsk.Enabled = false;
            }
            else
                UpdateForm();
        }
    }

The Game runs fine, but my question here is , I can't understand how the method GetWinnerName( ) in the class Game is working

 

In this loop

 foreach (Values value in books.Keys)
            {
                string name = books[value].Name; 
                if (winners.ContainsKey(name)) //What is ContainsKey ?
                    winners[name]++; // What is happening here ?
                else
                    winners.Add(name, 1); // What is happening here ?
            }

 

 

[Andre S. Veteran]

A System.Collections.Generic.Dictionary is a Hash table. It can be seen as a collection of keys each mapping to a particular value, allowing for fast (usually O(1)) retrieval of the associated value given the key, using a hash of the key (hence why every object in .NET has a GetHashCode() method).

 

As the name suggests, ContainsKey is a method that returns true if the Dictionary contains the specified key and false otherwise.

 

On this line,

winners[name]++

The value associated with the key name is retrieved and then incremented by one.

 

And here:

winners.Add(name, 1); 

The key-value pair [name, 1] is added to the collection. So now if you access it at name, you get 1 back.

[Ch33f]

On 4/23/2017 at 6:54 AM, Andre S. said:

A System.Collections.Generic.Dictionary is a Hash table. It can be seen as a collection of keys each mapping to a particular value, allowing for fast (usually O(1)) retrieval of the associated value given the key, using a hash of the key (hence why every object in .NET has a GetHashCode() method).

 

As the name suggests, ContainsKey is a method that returns true if the Dictionary contains the specified key and false otherwise.

 

On this line,

winners[name]++

The value associated with the key name is retrieved and then incremented by one.

 

And here:

winners.Add(name, 1); 

The key-value pair [name, 1] is added to the collection. So now if you access it at name, you get 1 back.

Thank you