do-while loop doesn't work

for some reason my do-while implementation doesn't work. here is my code:

Code:

---

#include <stdio.h>

char getAns (char mesg[])
{
        char ans;
        printf ("&#37;s", mesg);
        ans = getchar();
        getchar();
        return toupper(ans);
}

void swap(int *p, int *q)
{
    int tmp;
       
    tmp = *p;
    *p = *q;
    *q = tmp;
}

void bubble (int a[], int N)
{
        int i, j;
       
        for (i = 0; i < N; i++)
                for (j = N - 1; i < j; j--)
                if (a[j - 1] > a[j])
                        swap(&a[j - 1], &a[j]);
}

int        main (void)
{       
        char ans;
        int i, N;
        int a[N + 1];
        do
        {
        printf ("Enter the amount of numbers to be sorted: ");
        scanf ("%d", &N);
        printf("Now enter the numbers:\n");
        for (i = 0; i < N; i++){
                scanf ("%d", &a[i]);}
        bubble (a, N);
        for (i = 0; i < N; i++)
        printf("%d ", a[i]);
        printf("\nYour numbers were sorted using BubbleSort.\n");
        ans = getAns ("\nSort again (Y/N) ?");
        } while (ans == 'Y');
        return 0;
}

---

thanks for any suggestions

>return toupper(ans);
You need to include <ctype.h> for this function.

>int i, N;
>int a[N + 1];
That's wrong on multiple levels. First, N hasn't been initialized, yet it's an automatic variable. The value is indeterminate. Second, unless you're using C99, you can't use a non-constant value as the size for an array.

Quote:

---

Originally Posted by Prelude

>int i, N;
>int a[N + 1];

That's wrong on multiple levels. First, N hasn't been initialized, yet it's an automatic variable. The value is indeterminate. Second, unless you're using C99, you can't use a non-constant value as the size for an array.

---

ok i added <ctype.h>...and yes i do realize that it was a stupid mistake, but the loop still doesn't work. Before i added the loop my program worked fine. Regarding the int i, N, i am not sure what C version i am using; since compiler gave no warnings and program functioned fine i assumed i made no big mistakes in the code.

You're mixing scanf with getchar.

Your last scanf leaves a \n on the input stream
Your first getchar reads that \n
Result, You're here asking a question.

Several FAQs deal with reading input. Concentrate on the ones which read input using fgets().

ok cheers now it works. i swapped:
ans = getchar();
getchar();

for:
getchar();
ans = getchar():

and it works. thanks a lot

Try typing a space after the last number you input.

"Works" is entirely subjective, because as far as I can tell, you've just swept the problem under the carpet.

Your program is perfect in every way.

It's not. For a perfect program, I'd say get rid of scanf to read input since it's so error prone to leave crap in the input buffer. The program doesn't check if there's anything left in the input buffer either, so it's a walking time bomb, or rather, it's just luck that the program works as expected.

Btw, a tip for you: indent each block once and once only. Each if, each while, and each line of code after those should be indented once more. And it's not truly wise to mix spaces and tabs. Use one.

Quote:

---

Originally Posted by Link_26

Your program is perfect in every way.

---

That can only have been sarcasm, meant to imply the opposite.

A rather poor sarcasm, though, since it doesn't even say what's wrong.

but ELYSIA how can you completely eliminate scanf from your program when getchar() is extremely cumbersome to use..
so it would be better to use fflush to flush out the buffer before using getchar() or any other related input function
isnt it??????

Quote:

---

Originally Posted by ElemenT.usha

but ELYSIA how can you completely eliminate scanf from your program when getchar() is extremely cumbersome to use..

---

Quote:

---

Originally Posted by Salem

Several FAQs deal with reading input. Concentrate on the ones which read input using fgets().

---

--------------------------------

Quote:

---

Originally Posted by ElemenT.usha

so it would be better to use fflush to flush out the buffer before using getchar()

---

lulz.

Use fgets. No messy input buffer. Reads everything and doesn't leave anything dangling in the input. Read FAQ.

Quote:

---

Originally Posted by zx-1

--------------------------------


lulz.

---

so i dint get you my friend... what was lolz about??????

The implication of using fflush() on the stdin stream.

oops i am sorry.... my mistake..... so the need of using fscanf()

What are you babbling about?
fscanf, scanf, they're all the same.
Use FGETS. Read the FAQ for more information!
And don't use fflush on stdin. It's undefined. Again, read the FAQ.

oh my apologies on that