node *head=NULL,*tail=NULL,*p,*q;

                  if(q==p)
                    {
                        head=NULL;
                        delete p;
                    }
                    else
                        delete_node(q,p);





void delete_node(node *q,node *p)//{
    while(q->next!=p)//
    {
        q=q->next;
    }
    if(p->next)
        q->next=p->next;//
    else
        q->next=NULL;//
    delete p;//
}
截取程序的代码，请问，这几句怎么理解，帮我写下注释好么？谢谢