双向链表

定义

typedef struct DulNode
{
	ElemType data;
	struct DulNode *prior;
	struct DulNode *next;
} DulNode, *DuLinkList;

在p指针所指节点之后，插入的关键步骤：

s->prior = p;
s->next = p->next;
p->next->prior = s;
p->next = s;

删除p指针所指节点的关键步骤：

p->prior->next = p->next;
p->next->prior = p->prior;
free(p);