/* Nonrecursive delete of list item */

typedef struct node 
{   struct node *next;
    int number;
}  NODE, *PNODE;
    
/* (non-recursive) delete of all linked list items with number field n */
/* returns pointer to starting node of new list */

PNODE delete_node(PNODE pnode, int n)
{
    PNODE pnext,pdone;
    
    if (pnode == NULL) return NULL; /* empty list - nothing to delete */

    /* when node to delete is at beginning of list */
    while (pnode->number == n)
    {
	pnext = pnode->next;	/* save location of next node */
	free(pnode);
	pnode = pnext;
	if (pnode == NULL) return NULL; /* check if list has become empty */
    }
    
    /* when node to delete is no longer at beginning of list */
    pdone = pnode;      /* pdone - node up to which deletes have been done */
    while ((pnext = pdone->next) != NULL)
    {
	if (pnext->number == n)
	{
	    pdone->next = pnext->next; /* remove pnext node */
	    free(pnext);
	}
	else pdone = pnext;
    }
    return pnode;
}

/* ** Some ways to advance down a list ** */
    
/* inline code */
if (pnode != NULL) pnode = pnode->next;

/* macro    - usage:  advance(pnode);  */
#define advance(x) ((x) != NULL ? (x) = (x)->next : NULL)

/* function - usage:  pnode = advance(pnode); */
PNODE advance(PNODE pnode)
{
    if (pnode != NULL) return pnode->next;
    else return NULL;
}

/* function - usage:  advancep(&pnode); */
void advancep(PNODE *ppnode)
{
    if (*ppnode != NULL) *ppnode = (*ppnode)->next;
}