From:	"John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Linked lists (please don't kill me!)
Date:	Sun, 15 Jun 1997 14:25:53 +0000
Organization:	Two pounds of chaos and a pinch of salt
Lines:	163
Message-ID:	<33A3FB71.2E1A@cs.com>
References:	<33A3D1BF DOT 6BCC AT maties DOT sun DOT ac DOT za>
Reply-To:	fighteer AT cs DOT com
NNTP-Posting-Host:	ppp110.cs.com
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

sar AT maties DOT sun DOT ac DOT za wrote:
> 
> I'm a newbie to DJGPP and C itself. Can anybody provide me with some
> sample code as to how to create, modify and erase linked lists under
> DJGPP? I know it has something to do with pointers but I just can't seem
> to get the syntax and the * in the right places.

comp.lang.c and comp.lang.c.moderated are better places to ask this
question.  This newsgroup is not for basic programming questions.  Also,
if your C textbook doesn't tell you how to make a linked list, you
should burn it and buy a better one.

Just so you don't go away mad:

/* basic linked list */

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

typedef struct item_data	ITEM;
typedef struct node_data	NODE;
typedef NODE *			LIST;

struct item_data
{
    char name[30];
    char address[40];
};

struct node_data
{
    ITEM item;
    NODE *next;
};

int Add_Node( LIST *list, ITEM item );
int Delete_Node( LIST *list, NODE *node );

/* adds node to the list containing the data in item.
   returns nonzero on success; 0 on failure */
int Add_Node( LIST *list, ITEM item )
{
    NODE *new;

    if ( ( new = (NODE *) malloc( sizeof(NODE) ) ) == NULL )
    {
        fprintf( stderr, "Add_Node: out of memory.\n" );
        return 0;
    }
    new->item = item;

    new->next = *list;
    *list = new;

    return 1;
}

/* removes node from the list and frees the memory it uses.
   returns nonzero on success, 0 on failure */
int Delete_Node( LIST *list, NODE *node )
{
    NODE *temp;

    if ( *list == NULL )   /* list is empty */
        return 0;

    if ( *list == node )
    {
        *list = node->next;
        free( node );
        return 1;
    }

    for ( temp = *list; temp->next != NULL; temp = temp->next )
        if ( temp->next == node )
        {
            temp->next = node->next;
            free( node );
            return 1;
        }

    return 0;  /* node not found */
}

/* example of usage */

int main( void )
{
    LIST the_list = NULL;
    NODE *temp;
    ITEM customer;
    int done = 0;
    int answer, count;;

    while( !done )
    {
        clrscr( );
        printf( "%3s  %-30.30s  %-40.40s\n", "ID", "Name",
                "Address" );
        for ( count = 1, temp = the_list; temp != NULL; count++, temp =
temp->next )
            printf( "%3d  %-30.30s  %-40.40s\n", count,
                    temp->item.name, temp->item.address );

        printf( "1 - Add customer\n2 - Delete customer\n3 - Quit\n" );
        printf( "Selection?  " );
        scanf( "%d", &answer );
        while( getchar( ) != '\n' )
            ;

        switch( answer )
        {
        case 1:
            /* using gets here is very bad - typing more characters
               than size of string may cause crashes/bad data.
               Fixing this is an exercise for the reader. */
            printf( "Name:  " );
            gets( customer.name );
            printf( "Address:  " );
            gets( customer.address );
            if ( Add_Node( &the_list, customer ) == 0 )
            {
                printf( "Unable to add customer!\n" );
                getch( );
            }
            break;

        case 2:
            printf( "# of customer to delete?  " );
            scanf( "%d", &answer );
            while( getchar( ) != '\n' )
                ;

            for ( count = 1, temp = the_list; temp != NULL; temp =
temp->next, count++ )
                if ( count == answer )
                    break;
            if ( temp == NULL )
                break;
            if ( Delete_Node( &the_list, temp ) == 0 )
            {
                printf( "Unable to delete customer!\n" );
                getch( );
            }
            break;

        case 3:
            done = 1;
            break;
        }
    }

    return 0;
}

-- 
---------------------------------------------------------------------
|      John M. Aldrich       | "A woman is not property, and hus-   |
|       aka Fighteer I       | bands who think otherwise are living |
|   mailto:fighteer AT cs DOT com   | in a dreamworld."                    |
| http://www.cs.com/fighteer |                - Lazarus Long        |
---------------------------------------------------------------------

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