.. _topic7-example:

Example - Linked Lists
=========================


Append To a List
-----------------

::

    typedef struct list {
        int data;
        struct list *next;
    } LIST;
    
    
    LIST *append( LIST *start, int newdata )
    {
        LIST *new, *end, *ret;
    
        if( (new = (LIST *)malloc(sizeof(LIST))) == NULL) {
            fprintf( stderr, "Memory Allocation error.\n" );
            return 1;
        }
        if( start == NULL ) 
            ret = new;
        else {
            ret = start;
            end = start;
            while( end->next != NULL ) end = end->next;
            end->next = new;
        }
        new->data = newdata;
        new->next = NULL;
        return( ret );
    }


Delete From a List
-----------------------

::

    LIST *remove( LIST *start, LIST *remove )
    {
        LIST *previous, *ret;
    
        if( remove == NULL || start == NULL ) return( NULL );
        if( remove == start ) {
            ret = remove->next;
            free( remove );
            return( ret );
        }
        previous = start;
        while( previous->next != remove && previous->next != NULL )
            previous = previous->next;
        if( previous->next != NULL ) { /* item found in list */
            previous->next = remove->next;
            free( remove );
        }
        return( start );
    }


.. _sort_insert:

Sorted Insert To a List
-------------------------

.. index:: Insertion sort

::

    LIST *insert( LIST *start, int newdata )
    {
        LIST *new, *next, *previous, *ret;
    
        if( (new = (LIST *)malloc(sizeof(LIST))) == NULL) {
            fprintf( stderr, "Memory Allocation error.\n" );
            return 1;
        }
        if( start == NULL ) {
            ret = new;
            new->next = NULL;
        }
        else {
            next = start;
            previous = NULL;
            while( next->data < newdata && next != NULL ) {
                previous = next;
                next = next->next;
            }
            new->next = next;
            if( previous == NULL )
                ret = new;
            else {
                previous->next = new;
                ret = start;
            }
        }
        new->data = newdata;
        return( ret );
    }