How come my straight counter remains at a value of zero?

Question

I am making a program in the C90 standard using GCC in Ubuntu 10.04, that randomly generates a hand of 5 card structs and calculates if the hand is a flush, straight, etc.

My function to calculate straights is:

int isStraight(card hand[]) {
    int i, count = 1, result = 0;
    for (i = 0; i < HAND_SIZE-1; i++) {
        if (hand[i].pips == ((hand[i+1].pips) + 1)) {
            count++;
        }
    }
    if (count == HAND_SIZE)
        result = 1;
    return result;
}

My main function:

int main(void) {

    int i, j;
    int numHands = 0;
    int flushCount = 0;
    int straightCount = 0;
    int xOfAKindCount = 0;
    int straightFlushCount = 0;
    int fullHouseCount = 0;
    int isTwoPairCount = 0;

    card deck[DECKSZ] = {0};
    card hand[HAND_SIZE] = {0};

    stack deckStack = {0};
    stack handStack = {0};

    initDeck(deck);
    shuffleDeck(deck);
    reset(&deckStack);

    for (i = 0; i < DECKSZ; i++) {
        push(deck[i], &deckStack);
    }

    do {
        reset(&handStack);
        for (i = 0; i < HAND_SIZE; i++) {
            push(pop(&deckStack), &handStack);
            if (isEmpty(&deckStack)) {
                reset(&handStack);
                shuffleDeck(deck);
                reset(&deckStack);
                for (j = 0; j < DECKSZ; j++) {
                    push(deck[j], &deckStack);
                }
            }
                hand[i] = handStack.s[i];
            }

        numHands += 1;
        arrangeHand(hand);

        flushCount += isFlush(hand);
        straightCount += isStraight(hand);
        xOfAKindCount += isXOfAKind(hand, 2, 0);
        straightFlushCount += isStraightFlush(hand);
        fullHouseCount += isFullHouse(hand);
        isTwoPairCount += isTwoPair(hand);

        printf("Flushes:%d Straights:%d SF's:%d Number of Hands:%d\r",
            flushCount, straightCount, straightFlushCount, numHands);
    } while (1);

    printf("\n");

    return EXIT_SUCCESS;
}

My issue is my variable declared inside my function, result, is never set to 1 to indicate whether or not the hand is a straight, which therefore means my straightCount variable always remains at a value of zero. I do not have access to a debugger and in my mind the code I have makes sense. I'm new to programming in C, so if anybody could help me point out what is wrong with my function, I'd appreciate it. Thanks!

Answer 1

int isStraight(card hand[]) {
  int step = 0;
  for(int i = 1;i < HAND_SIZE; i++)
    if(hand[i].pip != hand[i-1].pip+1)
      /* Substitute step with i!=1 if over-edge invalid */
      if(step || hand->pip != 1 || hand[i].pip != hand[i-1].pip+13-HAND_SIZE)
        return 0;
      else
        step = 1;
  return 1;
}

Answer 2

Right, after reading the code again, there are not enogh cards...

 for (i = 0; i < HAND_SIZE-1; ++i)

Then you care counting pairs, not just individual cards, so

  If (count == HAND_SIZE-1)

Answer 3

for (i = 0; i < HAND_SIZE-1; i++) { means that you are testing HAND_SIZE-1 pairs (which is correct), with i from from 0 to HAND_SIZE-2, so count will never be HAND_SIZE.

You just need to change your test to if (count == HAND_SIZE-1)

Answer 4

Assuming that (a) pip values are 1=Ace, 2=Deuce, ... and (b) the hand is sorted before being passed to the function, and (c) hands are exactly five cards, here's a quick one:

int isStraight(card hand[]) {
    int i;
    // Handle Broadway special case
    if (hand[0].pips == 13 && hand[1].pips == 12 && hand[2].pips == 11 &&
        hand[3].pips == 10 && hand[4].pips == 1) return 1;

    // This will handle the rest
    for (i = 0; i < (HAND_SIZE-1); i += 1) {
        if (hand[i].pips != hand[i+1].pips) return 0;
    }
    return 1;
}

Also, I wouldn't use a structure for cards. Using a single integer is much faster and more versatile. Check out http://etceterology.com/blog/2013/5/23/representing-playing-cards-in-software