shuffling a vector

[Xendraw]

hey guys, i am at a loss about how to simply swap the contents of a vector to give a 'random shuffle' do you guys have any examples or ideas that may work?

[Athar]

std::random_shuffle(vec.begin(),vec.end());
Implementation is here: http://www.cplusplus.com/reference/algorithm/random_shuffle/

[Xendraw]

i dont quite understand how that works, saying i had a vector called 'vec' how would i be able to create 1 function for shuffling?

[Athar]

The function already exists, so just call it.

[Xendraw]

so what you wrote up there is a function?

[Athar]

No, it's a function call. See http://www.cplusplus.com/reference/algorithm/random_shuffle/

[Xendraw]

it doesnt really explain how it is working though

[Athar]

...
Yes, it does. The implementation is right on that page:

for (i=n-1; i>0; --i) swap (first[i],first[rand(i+1)]);

And the explanation is right there too:

The function swaps the value of each element with that of some other randomly chosen element. When provided, the function rand chooses which element.

[Xendraw]

ah ok, i see now, but i just need it all to fit in one function in a class, the example here shows more than one

im having abit of trouble applying it to my vector

[Athar]

shows more than one

Shows more than one what?

[Xendraw]

function

sorry, i haven't been too clear here, i am trying to shuffle a deck of cards, i need the function to shuffle the vector 'pcardvector'

something like this:

void shufflecards ()
            {
                srand ( time(NULL) );

                random_shuffle(pcardvector.begin(),pcardvector.end());
            }

just not sure how to implement it

[Athar]

just not sure how to implement it

You already did?
Except that the srand call belongs to the beginning of main.

[Xendraw]

but it isnt shuffling, i have a function that prints the vector, and after using the 'shuffle function, it stays the same

[Athar]

It doesn't (except by pure chance). Show your full code.

[Xendraw]

my main:

#include <iostream>
#include <string>
#include <ctime>
#include <cstdlib>
#include <vector>
#include <list>
#include <algorithm>
#include <functional>
#include "class.cpp"
#include "deck class.cpp"

using namespace std;

vector<Card> deck1;
/** this void function creates a vector of 'card' objects using the push_back
     function*/
void createDeck()
{
    int n,i,j;
    string b;
    j = 0;

    for(n = 0; n < 4; n++)
    {
        for(i = 1; i < 14; ++i)
        {
            switch (n)
            {
                case 0: b = "Hearts";
                break;

                case 1: b = "Spades";
                break;

                case 2: b = "Diamonds";
                break;

                case 3: b = "Clubs";
                break;
            };

            deck1.push_back(Card(i, b));

        }
    }

}

/** i have placed the above created deck as the argument for the deck class
    constructor, and called for the printdeck function to be used.*/
int main()
{
    srand ( time(NULL) );
    createDeck();
    Deck(deck1).printdeck();
    Deck(deck1).shufflecards();
    Deck(deck1).printdeck();
    return 0;
}

my deck class:

#include <iostream>
#include <string>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <algorithm>
#include <functional>

using namespace std;

class Deck
{
        /** these private vectors are the deck, and the pointers to the deck */
    private: vector<Card> cardvector; vector<Card *> pcardvector;

    public:
    /** this constructor also uses a for loop to create a pointer for each card */
            Deck (vector<Card> cardvector2)
            {
                cardvector = cardvector2;

                for (size_t x = 0; x < cardvector.size(); ++x)
                {
                    pcardvector.push_back(&cardvector[x]);
                }
            }
/** by printing with the pointers, it allows me to shuffle the pointers later on
rather than the actual deck, this is good because i still have my original deck.
 */
            void printdeck ()
            {
                for (size_t x = 0; x < pcardvector.size(); ++x)
                {
                    switch(pcardvector[x]->getvalue())
                    {
                        case 1: cout << "Ace"; break;

                        case 11: cout << "Jack"; break;

                        case 12: cout << "Queen"; break;

                        case 13: cout << "King"; break;

                        default: cout << pcardvector[x]->getvalue(); break;
                    }
                    cout << " of ";
                    cout << pcardvector[x]->getsuit() << endl;

                }cout << endl;
            }

            void nextcard ()
            {

            }

            void shufflecards ()
            {
                random_shuffle(pcardvector.begin(),pcardvector.end());
            }
};

my card class:

#include <iostream>
#include <string>

 using namespace std;

 class Card
{
    private: string suit; int value;

    public:
            Card()//default constructor (no arguments) allows you to make an
            {     //array
                value = 0;
            }

            Card(int v, string s)// allows the private attributes to be set
            {
                value = v;
                suit = s;
            }

            int getvalue()// returns the cards value
            {
                return value;
            }

            string getsuit()// returns the cards suit
            {
                return suit;
            }
};

[Athar]

Deck(deck1).printdeck();
Deck(deck1).shufflecards();
Deck(deck1).printdeck();

You create a temporary copy of deck1, print it, then you create another temporary copy of deck1 and shuffle it, then you create another temporary copy of deck1 and print it.

Edit: make that "a temporary instance of Deck that copies the deck1 vector" in all three cases.

[Xendraw]

how would i get past that?? also, how are they temporary?

[Moschops]

Deck(deck1)

This creates a new object of type Deck, which will be a copy of deck1. It's temporary because you've not given it a name.

If you want to shuffle the actual deck1, try

deck1.shufflecards();

[Xendraw]

isnt its name deck1? and that wont work cause there is no shufflecards in the card class

[Peter87]

deck1 is not a Deck so that will not work.

First create a named Deck object
Deck deck(deck1);
You can then call the functions like this:
deck.shufflecards();