双链表的销毁

typedef struct dnode
{
        int data;
        struct dnode *prior;
        struct dnode *next;
}DNode;

void destroryDNode(DNode *head)
{
        DNode *p = head->next;
        DNode *q = NULL;
        DNode *r = NULL;
        for(q=p; q->next!=NULL; q=r)
        {
                r = q->next;
                free(q);
                q->next=NULL;
        }
        free(r);
        free(head);
        head=NULL;
}