Question

I’m fairly new to C++ and don’t quite understand function parameters with pointers and references. I have an array of Cards that I want to shuffle using the Fisher-Yates shuffle. The deck is declared as

Card *deck[deckSize];

where deckSize has been declared as 24. The array is then initialized.
I then call the shuffle function:

void shuffle (Card * deck[]) {
    int deckSize = 24;
    while (deckSize > 1) {
       long int k = lrand48();
       k = k %24;
       deckSize--;
       Card * temp = deck[deckSize];
       deck[deckSize] = deck[k];
       deck[k] = temp;
    }
}

If I try to print the value of a card after calling the shuffle function I get a seg fault. Any pointers on how to do this properly?

Answer 1

It looks that your problem does not come from the code posted, which looks fine at a first glance, but from the code around it.

What about using a standard container of cards ? You must fill it, print it first to see if it’s ok, shuffle, and then print it again.

#include <vector>
std::vector<Card> deck; // Empty for now. Must be filled with cards.


void shuffle (std::vector<Card> & deck)
{
    int deckSize = 24;
    while (deckSize > 1) 
    {
       long int k = lrand48();
       k = k %24;
       deckSize--;
       Card temp = deck[deckSize];
       deck[deckSize] = deck[k];
       deck[k] = temp;
    }
}