双向链表

插入操作：

传入指向根节点的指针

current指针，next指针遍历操作

current指向新节点，newnode指向next

向后指针需要分情况，是否为跟节点，是否为尾部

typedef struct doublenode
{
	struct doublenode *fwd;
	struct doublenode *bwd;
	int date;
}DOUBLE_NODE_STRUCT;

int insert_double_node(DOUBLE_NODE_STRUCT *rootp,int value)
{
	DOUBLE_NODE_STRUCT *newDate;
	DOUBLE_NODE_STRUCT *current;
	DOUBLE_NODE_STRUCT *next;

	for (current = rootp; (next = current->fwd) != NULL; current = next->fwd)
	{
		if (next->date == value)
		{
			return 0;
		}
		if(next->date > value)
		{
			break;
		}
	}
	
	newDate = (DOUBLE_NODE_STRUCT *)malloc(sizeof(DOUBLE_NODE_STRUCT));
	if (newDate == NULL)
	{
		return -1;
	}
	newDate->date = value;

	current->fwd = newDate;
	newDate->fwd = next;

	if (current == rootp)
	{
		newDate->bwd = NULL;
	}
	else
	{
		newDate->bwd = current;
	}
	if (next == NULL)
	{
		rootp->bwd = newDate;
	}
	else
	{
		next->bwd = newDate;
	}
	return 1;
}

遍历操作

	int iResult = true;
	DOUBLE_NODE_STRUCT rootNode =
	{
		NULL,
		NULL,
		0
	};
	iResult = insert_double_node(&rootNode, 2);
	iResult = insert_double_node(&rootNode, 4);
	iResult = insert_double_node(&rootNode, 1);
	iResult = insert_double_node(&rootNode, 6);
	//正向
	for (DOUBLE_NODE_STRUCT * current = &rootNode; current->fwd != NULL; current = current->fwd)
	{
		printf("%d\n",current->fwd->date);
	}
	//反向
	for (DOUBLE_NODE_STRUCT *current = &rootNode; current->bwd != NULL; current = current->bwd)
	{
		printf("%d\n",current->bwd->date);
	}

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