Increment/Decrement operator troubles

I have this bubble sort code that is just supposed to sort elements of an array in ascending order:

Code:

#include <stdio.h>

int main(void)
{
    int i = 0, didSwap = 0, temp = 0, inner = 0, outer = 0;
    char buffer[100] = {0};
    int firstArray[10] = {0};

    for (i = 0; i < 10; ++i)
    {
        printf("firstArray[%d]: ", i);
        fgets(buffer, sizeof(buffer), stdin);
        sscanf(buffer, "%d", &firstArray[i]);
    }

    for (outer = 0; outer < 9; outer++)
    {
        didSwap = 0;

        for (inner = outer; inner < 10; inner++)
        {
            if (firstArray[inner] < firstArray[outer])
            {
                temp = firstArray[inner];
                firstArray[inner] = firstArray[outer];
                firstArray[outer] = temp;
                didSwap = 1;
            }
        }

        if (didSwap == 0)
            break;
    }

    for (i = 0; i < 10; ++i)
        printf("\nfirstArray[%d] = %d", i, firstArray[i]);

    return (0);
}

The sorting works fine when the increment operators inner++ and outer++ are in postfix form. However, when I change it to prefix form ++inner and ++outer it no longer sorts. I always thought that it didn't matter which form you used in the third part of a for statement.

Can someone enlighten me on to why this happens? Thanks in advance.

If you mean only changing this:

Code:

    for (outer = 0; outer < 9; outer++)
    {
        /* ... */
        for (inner = outer; inner < 10; inner++)

to this

Code:

    for (outer = 0; outer < 9; ++outer)
    {
        /* ... */
        for (inner = outer; inner < 10; ++inner)

I notice no difference.

Increment and decrement operators when taken as a single statement, behave the same regardless of prefix or postfix. The last segment, as Dave mentioned, of your for loop is considered a single statement as you are currently using it, and as such, the result is the same.

Code:

i++;
++i;

The above two lines have the same result. The difference you'll see is when you do things like:

Code:

x = a[ ++i ];
x = a[ i++ ];
fun( i++ );
fun( ++i );

Things like that.


Quzah.

Dave_Sinkula, yes, I did mean that. For some reason when I compile it using prefix form it refuses to sort.

Quzah, I thought that was how it worked, but something seems to be wrong in my case.

Maybe my compiler is messing something up? I'm using Code::Blocks with MingW. I don't know what else could be the problem.

Thanks for the replies.

Originally Posted by LineOFire

Maybe my compiler is messing something up? I'm using Code::Blocks with MingW. I don't know what else could be the problem.

When you're new, save that until the very last. (That also happens to be what I used to check both forms.)

Perhaps post the result(s) of your attempt(s)?

You could post your prefix code. It's rare to have a compiler bug of this nature.

Never mind this post. I don't know what happened but it is working like it should now, even using the prefix form. I probably forgot to save before recompiling or something.

Glad to realize it was human stupidity and not compiler error because Code::Blocks certainly is excellent.

Thanks for the replies.