Question about vector/deque

This is a discussion on Question about vector/deque within the C++ Programming forums, part of the General Programming Boards category; As you might know I am pretty knew to using the STL I just started looking at it a couple ...

  1. #1
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    Question about vector/deque

    As you might know I am pretty knew to using the STL I just started looking at it a couple of days ago. Anyway...
    I have two deques. One is my deck of cards (52 elements) the other is my hand which is empty on creation.
    I want to take N cards from the deck and put them into my hand.
    I am so confused as to how to do this I need to see an example of how to copy an element of one deque to another.

    This is what I feel like doing, but it is pretty obvious that it wont work.
    Code:
    void draw_cards(deque<Cards> *hand, deque<Cards> *deck, int num){
      
      for(int i=0;i<num;i++){
        hand->push_front( /*deck[i] element to be inserted here */);
        deck->pop_front();
    
      } 
     
    }
    I am so lost

  2. #2
    aoeuhtns
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    Replace /*deck[i] element to be inserted here */ with deck[0]

    This pushes a copy of the first card of the deck into your hand. Then pop_front removes the first card. Then you push the first card of the deck (which used to be the second card) into your hand. Then pop_front removes the first card. Now on top of the deck lies what was originally the third card.

  3. #3
    Tropical Coder Darryl's Avatar
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    I would suggest instead of removing cards from the deck, you just create an index to where you are in the deck. That way you don't have to recreate the deck every hand, just reset the position and re-shuffle your deck.

    that way your method will work, just replace the pop_front with a line to increment you position index.

  4. #4
    Registered User Codeplug's Avatar
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    "deck[0]" is index 0 of an array of deque<Card> objects.......oops.

    It's better to prefer reference parameters over pointer paramters (plus a few other C++ idioms):
    Code:
    template<typename T>
    void draw_cards(deque<T> &hand, deque<T> &deck, typename deque<T>::size_type num)
    {
        assert(deck.size() >= num);
    
        typename deque<T>::size_type i = 0;
        for (; i < num; ++i)
        {
            hand.push_front(deck[0]);
            deck.pop_front();
        }//for
    }//draw_cards
    gg

  5. #5
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    This works. I didn't use Codeplug's example because right now im trying not to over confuse myself.
    Code:
    void draw_cards(deque<Cards> &hand, deque<Cards> &deck, int num){
      for(int i=0;i<num;i++){
        hand.push_front(deck[0]);
    
        deck.pop_front();
      }  
    }
    What I didn't think about was that deck[0] will be a different element every iteration because of the pop_front()

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