Not sure why I'm getting a segmentation fault when shuffling cards in C

Question

I know it has to do with my pointer variable, my goal is to implement the color of the suit to the preexisting code I was given. So I created a char pointer under the deck structure. It will print out everything correctly until I get to shuffle, in which case I get a segmentation fault.

 #include <stdio.h>
 #include <time.h> //time function
 #include <stdlib.h> //random number generator functions
 #include <string.h> //need for Linux

 #define MAX 9
 #define MAX_CARDS 52
 #define MAX_RANKS 13
 #define MAX_SUITS 4
 #define COLS 2 //number of columns to display in output

//structure definition
struct card{
char *rank;
char suit[MAX];
char *color;
};
typedef struct card Card;

//array of pointers to strings for ranks
char *ranks[MAX_RANKS] = {"Ace", "Two", "Three", "Four", "Five", "Six",     "Seven",
"Eight", "Nine", "Ten", "Jack", "Queen", "King"};

char *color[2] = {"(black)", "(red)"};

//two-dimensional array of strings for suits
char suits[MAX_SUITS][MAX] = {"Clubs", "Diamonds", "Hearts", "Spades"};
//[0][1] [0][2][0][3]

void initialize(Card []);
void shuffle(Card []);
void display(const Card[]);

int main(){
char newline = '\n'; //to repeat while loop
//declare an array of 52 cards

Card deck[MAX_CARDS] = {"","",""};
initialize(deck);
deck[0].color = "(black)" ;
deck[1].color = "(red)";
printf("Display an ordered deck of cards:\n");
display(deck);
while('\n' == newline){
    printf("\nshuffling deck ... \n\n");
    shuffle(deck);
    display(deck);
    printf("\n\nWould you like to shuffle again?\nIf so, press        \"Enter\" key. If not, enter any other char. ");
    newline = getchar();
}
    return 0;
}

/*
 initialize the deck of cards to string values
 deck: an array of structure cards
 */
void initialize(Card deck[]){
    int i = 0;
    for(i=0;i<MAX_CARDS;i++){
        deck[i].rank = ranks[i%MAX_RANKS];
        strncpy(deck[i].suit, suits[i/MAX_RANKS], MAX);
    }
}

/*
 use the pseudo-random number generator to shuffle the cards
 deck: an array of structure cards
 */
void shuffle(Card deck[]){
    int swapper = 0; //index of card to be swapped
    int i = 0; //counter
    Card temp = {"", ""}; //temp holding place for swap
    srand(time(NULL)); //seed the random numbers with current time
    for(i=0;i<MAX_CARDS;i++){
        //generate a pseudo-random number from 0 to 51
        swapper = rand() % MAX_CARDS;
        //swap current card with da swapper
        temp = deck[i];
        deck[i] = deck[swapper];
        deck[swapper] = temp;
    }
}

/*
 display the deck of cards
 deck: an array of structure cards 
 */
void display(const Card deck[]){
    int i = 0;
    for(i=0;i<MAX_CARDS;i++)
    {
        printf("%5s of %-10s", deck[i].rank, deck[i].suit);//%5s makes "of" line up -10 makes cols.
        if (strcmp(deck[i].suit, "Clubs") == 0 || strcmp(deck[i].suit, "Spades") == 0)
        {
            printf("     %5s", deck[0].color);
        }
         else
        {
            printf("      %5s", deck[1].color);
        }

        //put in a newline every %x loops
        if((COLS-1) == (i%COLS)){
            printf("\n");
        }

    }


}

Answer 1

This is because your cards have the color which you actually don't use, except here:

deck[0].color = "(black)" ;
deck[1].color = "(red)";

Now, when you shuffle the deck the chances are that you'd get another card there, whose .color is still NULL and your code crashes in printf("...%s...", deck[0].color);

The solution of course is to a) remove the color member altogether, b) then modify the printing code to

    if (strcmp(deck[i].suit, "Clubs") == 0 || strcmp(deck[i].suit, "Spades") == 0) {
        printf("     (black)");
    }
    else {
        printf("     (red)  ");
    }

---

However, I'd personally use enums to represent the ranks and suits, for example

enum Suit {
    HEARTS = 0, 
    SPADES, 
    DIAMONDS, 
    CLUBS
};

struct Card {
    enum Suit suit;
    ...
};

and for printing

char *suit_to_string[4] = {"Hearts", "Spades", "Diamonds", "Clubs"};

...
printf("%s", suit_to_string[deck[i].suit]);