Thread: scanf in bubblesort

  1. #1
    Registered User
    Join Date
    Dec 2007

    scanf in bubblesort

    here is my bubblesort code:
    #include <stdio.h>
    int N;
    void swap(int *p, int *q)
        int tmp;
        tmp = *p;
        *p = *q;
        *q = tmp;
    void bubble (int a[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)
    	int i;
    	int a[N];
    	printf ("Enter the amount of numbers to be sorted: ");
    	scanf ("%d\n", &N);
    	printf ("Enter your numbers:\n");
    	for (i = 0; i < N; i++){
    		scanf (" %d", &a[i]);}
    	bubble (a);
    	for (i = 0; i < N; i++)
    	printf("%d ", a[i]);
    	return 0;
    what i can't understand is why main only calls printf ("Enter your numbers:\n") after the for loop and not before it as it is so in the code. any suggestions? also any ideas on how to re-declare N so it is not a global variable?

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    Like I said in your previous thread, newlines in scanf calls do NOT do what you think they should.

    scanf ("&#37;d\n", &N);

    Also, this isn't the way to declare an N element array either.
    You need to set a maximum size when you declare the array, then decide how many values you want to input.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
    Join Date
    Oct 2007
    Inside my computer
    For your global var, just define it in main and pass it as argument to any function that needs it.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  4. #4
    Registered User
    Join Date
    Dec 2007
    ok cheers. i removed \n from scanf and it works now. yeah i do know that i didn't declare N properly. it has to be define N etc etc.

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