Code - Shuffle.c (called the Jumbler in the slides)

// Shuffle can read in a small deck of cards
// It will partially shuffle that deck
// then print out the new ordering of those cards

// Marc Chee (cs1511@cse.unsw.edu.au), October 2020

#include <stdio.h>

#define MAX_DECK_SIZE 52

int readInput(int deck[MAX_DECK_SIZE]);
void printDeck(int deck[MAX_DECK_SIZE], int currentDeckSize);
void swap(int *card1, int *card2);
void shuffle(int deck[MAX_DECK_SIZE], int currentDeckSize);

int main(void) {
    int deck[MAX_DECK_SIZE] = {0};
    int deckSize = readInput(deck);
    shuffle(deck, deckSize);
    printDeck(deck, deckSize);
}

// Read the input and store it in the array
// returns the exact number of cards read in
int readInput(int deck[MAX_DECK_SIZE]) {
    // ask the user how many cards there are
    printf("How many cards are you entering?\n");
    int num_cards = -1;
    scanf("%d", &num_cards);
    
    // loop through and scan in the cards
    int i = 0;
    while (i < num_cards && i < MAX_DECK_SIZE) { // have read i cards
        // write each number scanned into the array
        scanf("%d", &deck[i]);
        i++;
    } // have read i cards
    return i;
}

// print out the cards in the deck
void printDeck(int deck[MAX_DECK_SIZE], int currentDeckSize) {
    int i = 0;
    while (i < currentDeckSize) {
        printf("%d ", deck[i]);
        i++;
    }
    printf("\n");
}

// Shuffle will call the swap function multiple times
// on the deck
void shuffle(int deck[MAX_DECK_SIZE], int currentDeckSize) {
    int i = 0;
    while (i < currentDeckSize) {
        // otherCard is just a made-up way of
        // grabbing another "random" card
        int otherCard = (i * 2) % currentDeckSize;
        swap(&deck[i], &deck[otherCard]);
        i++;
    }
}

// Swaps the values stored in integers that
// card1 and card2 point at
void swap(int *card1, int *card2) {
    int temp = *card1;
    *card1 = *card2;
    *card2 = temp;
}