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up vote -4 down vote favorite

When I create an object of type Deck, an exception is shown: "indexoutofrangeexception was unhandled"

Can someone explain why?

public class Deck {
    Card[] card = new Card[52];
    const int NumOfCards = 52;

    public Deck()
    {
        string[] symbol = { "Diamonds", "Clubs", "Hearts", "Spades"};
        string[] rank = { "Ace", "Two", "Three", "Four", "Five", "Six", 
                          "Seven", "Eight", "Nine", "Jack", "Queen", "King"};

        for (int i = 0; i < card.Length; ++i)
        {
            /// this is the line with problem shown in debug                 
            card[i] = new Card(symbol[i / 13], rank[i % 13]);   
        }    
        Console.WriteLine(card.Length);
    }

    public void PrintDeck()  {
        foreach (Card c in card)
            Console.WriteLine(c);
    }
}
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3  
Check the i % 13 value, then count items in rank, then look for "Ten" –  zerkms Sep 9 '13 at 21:01
    
Pff Zerk, I feel bad for posting as an answer now :) –  Rawling Sep 9 '13 at 21:03
1  
@Rawling: put en.wikipedia.org/wiki/Off-by-one_error there and it will be fine :-) –  zerkms Sep 9 '13 at 21:03
1  
why the close vote? this is very good question for SO. –  Preet Sangha Sep 9 '13 at 21:05
    
symbol has an off-by-nine error. I wonder why the OP uses card.Length, but not symbol.Length and rank.Length. –  dcaswell Sep 9 '13 at 21:14

1 Answer 1

up vote -1 down vote accepted

The error is in line

card[i] = new Card(symbol[i / 13], rank[i % 13]);

In the sentence 

rank[i % 13]

when i is equal to 12, we got 12 % 13 = 12, and then rank[12] is an array position that not exists. To solve it, change rank[i % 13] by rank[i % 12]

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