双向链表的实现（C语言）

//定义一个结构体表示双向链表的指针
typedef struct ListNode {
	int data;
	struct ListNode* next;
	struct ListNode* prev;
}LTNode;
//初始化
LTNode* ListCreate() {
	LTNode* guard = (LTNode*)malloc(sizeof(LTNode));//开辟一块空间
	if (guard == NULL) {
		perror("malloc fail:");
		exit(-1);
	}
	guard->next = guard;
	guard->prev = guard;
	return guard;
}
//节点的创建
LTNode* BuyListNode(int x) {
	LTNode* node = (LTNode*)malloc(sizeof(LTNode));
	if (node == NULL) {
		perror("malloc fail");
		exit(-1);
	}
	node->next = NULL;
	node->prev = NULL;
	node->data = x;
	return node;
}
//双向链表的打印
void ListPrint(LTNode* phead) {
	assert(phead);
	printf("phead<=>");
	LTNode* cur = phead->next;//哨兵节点
	while (cur != phead) {
		//就是说只要链表中流动指针不返回到哨兵节点就会一直遍历
		printf("%d<=>", cur->data);
		cur = cur->next;
	}
	printf("n");

}
//双向链表的尾部插入
void ListPushBack(LTNode* phead, int x) {
	assert(phead);
	LTNode* newnode = BuyListNode(x);
	//首先找到当前的尾结点
	LTNode* tail = phead->prev;
	//当前尾结点的下一个节点指向新的节点
	tail->next = newnode;
	//新节点的前一个是当前的尾结点
	newnode->prev = tail;
	phead->prev = newnode;
	newnode->next = phead;
}
//双向链表的前部插入
void ListPushFront(LTNode* phead, int x) {
	assert(phead);
	LTNode* newnode = BuyListNode(x);
	newnode->next = phead->next;
	//先处理好newnode与首节点的下一个节点之间的关系
	newnode->next = phead->next;
	phead->next->prev = newnode;
	phead->next = newnode;
	newnode->prev = phead;
}
//判断链表是不是空链表
bool ListEmpty(LTNode* phead) {
	assert(phead);
	return phead->next == phead;
}
//双向链表的尾部删除
void ListPopBack(LTNode* phead) {
	assert(phead);
	assert(!ListEmpty(phead));
	LTNode* tail = phead->prev;
	LTNode* prev = tail->prev;
	prev->next = phead;
	phead->prev = prev;
	free(tail);
	tail = NULL;

}
//头删
void ListPopFront(LTNode* phead) {
	assert(phead);
	assert(!ListEmpty(phead));
	LTNode* first = phead->next;
	LTNode* second = first->next;
	phead->next = second;
	second->prev = phead;
	free(first);
	first = NULL;
}
//双向链表元素计数
size_t ListNode(LTNode* phead) {
	assert(phead);
	size_t n = 0;
	LTNode* cur = phead->next;
	while (cur != phead) {
		++n;
		cur = cur->next;

	}
	return n;
}
//查找
LTNode* ListFind(LTNode* phead, int x) {
	assert(phead);
	size_t n = 0;
	LTNode* cur = phead->next;
	while(cur != phead) {
		if (cur->data == x) {
			return cur;
		}
		cur = cur->next;
	}
	return NULL;
}
//在指定的位置之前进行插入
void ListInsert(LTNode* pos, int x) {
	assert(pos);
	LTNode* prev = pos->prev;
	LTNode* newnode = BuyListNode(x);
	prev->next = newnode;
	newnode->prev = prev;
	newnode->next = pos;
	pos->prev = newnode;
}
//删除pos位置的值
void ListErase(LTNode* pos) {
	assert(pos);
	LTNode* prev = pos->prev;
	LTNode* next = pos->next;
	prev->next = next;
	next->prev = prev;
	free(pos);
}
//销毁
void ListDestory(LTNode* phead) {
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead) {
		LTNode* next = cur->next;
		free(cur);
		cur = next;
	}
	free(phead);
}