完成在双循环链表结点p之后插入s的操作为:
p->next->prev=s;s->prev=p;s->next=p->next;p->next=s;
p->next->prev=s;p->next=s;s->prev=p;s->next=p->next;
s->prev=p;s->next=p->next;p->next=s;p->next->prev=s;
s->next=p->next;p->next->prev=s;s->prev=p;p->next=s;
不定项选择