链表--- 双向链表及其实现

双向带头链表
双向链表也叫双链表，是链表的一种，它的每个数据结点中都有两个指针，分别指向直接后继和直接前驱。所以，从双向链表中的任意一个结点开始，都可以很方便地访问它的前驱结点和后继结点。一般我们都构造双向循环链表。

实现代码如下：
带头双向循环链表：
接口：

#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
#include<string.h>
#include<malloc.h>

typedef int LTDataType;
typedef struct ListNode
{
	LTDataType _data;
	struct ListNode* _next;
	struct ListNode* _prev;
}ListNode;
typedef struct List
{
	ListNode* _head;
}List;


void ListInit(List* plist);         //创建一个链表
void ListDestory(List* plist);    //消除一个链表
void ListPushBack(List* plist, LTDataType x);   //尾插
void ListPopBack(List* plist);  //尾删
void ListPushFront(List* plist, LTDataType x);   //头插
void ListPopFront(List* plist);   //头删
ListNode* ListFind(List* plist, LTDataType x); //查找
// 在pos的前面进行插入
void ListInsert(ListNode* pos, LTDataType x);
// 删除pos位置的节点
void ListErase(ListNode* pos);  
void ListRemove(List* plist, LTDataType x); //移除
int ListSize(List* plist);  //节点个数
int ListEmpty(List* plist);  // 清空
void ListReverse(List* plist); //相反链表
void ListPrint(List* plist);

接口具体实现：

ListNode*BuyListNode(LTDataType x)
{
	ListNode* node = (ListNode*)malloc(sizeof(ListNode));
	node->_data = x;
	node->_next = NULL;
	node->_prev = NULL;
	return node;
}
void ListInit(List* plist)    //构建链表
{
	ListNode* head = BuyListNode(-1);
	assert(plist);
	head->_next = head;
	head->_prev = head;
	plist->_head = head;
}
void ListDestory(List* plist)  //判断链表
{
	ListNode* head = plist->_head;
	ListNode* cur = head->_next;
	ListNode* next = NULL;
	assert(plist);
	while (cur != head)
	{
		next = cur->_next;
		free(cur);
		cur = cur->_next;
	}
	free(head);
	head = NULL;
}
void ListPushBack(List* plist, LTDataType x)    //尾插
{
	ListNode*head = plist->_head;
	ListNode* tail = head->_prev;
	ListNode* newnode = BuyListNode(x);
	assert(plist);
	tail->_next = newnode;
	newnode->_prev = tail;
	newnode->_next = head;
	head->_prev = newnode;
}


void ListPopBack(List* plist)    //尾删
{
	ListNode*head = plist->_head;
	ListNode* tail = head->_prev;
	ListNode* tailprev = tail->_prev;
	assert(plist);
	free(tail);
	tailprev->_next = head;
	head->_prev = tailprev;

}

void ListPushFront(List* plist, LTDataType x)  //头插
{
	ListNode*head = plist->_head;
	ListNode* next = head->_next;
	ListNode* newnode = BuyListNode(x);
	assert(plist);
	head->_next = newnode;
	newnode->_next = next;
	newnode->_prev = head;
	next->_prev = newnode;
}

void ListPopFront(List* plist) //头删
{
	ListNode* head = plist->_head;
	ListNode* next = head->_next;
	ListNode* nextnext = next->_next;
	assert(plist);
	free(next);
	head->_next = nextnext;
	nextnext->_prev = head;

}


ListNode* ListFind(List* plist, LTDataType x)  //查找
{
	ListNode* head = plist->_head;
	ListNode* cur = head->_next;
	assert(plist);
	while (cur != head)
	{
		if (cur->_data == x)
		{
			return cur;
		}
		cur = cur->_next;
	}
	return cur;
}
// 在pos的前面进行插入
void ListInsert(ListNode* pos, LTDataType x)
{
	ListNode* prev = pos->_prev;
	ListNode* newnode = BuyListNode(x);
	assert(pos);
	newnode->_next = pos;
	pos->_prev = newnode;
	prev->_next = newnode;
	newnode->_prev = prev;
}
// 删除pos位置的节点
void ListErase(ListNode* pos)
{
	ListNode* prev = pos->_prev;
	ListNode* next = pos->_next;
	assert(pos);
	free(pos);
	prev->_next = next;
	next->_prev = prev;
}

void ListRemove(List* plist, LTDataType x)  //移除
{
	ListNode* node = ListFind(plist, x);
	assert(plist);
	if (node != plist->_head)
	{
		ListErase(node);
	}
}

int ListSize(List* plist)  //节点个数
{
	int size = 0;
	ListNode* cur = plist->_head->_next;
	assert(plist);
	while (cur != plist->_head)
	{
		size++;
		cur = cur->_next;
	}
	printf("%d", size);
	return size;

}
int ListEmpty(List* plist) //清空链表
{
	assert(plist);
	printf("%d", plist->_head->_next == plist->_head ? 0 : -1);
	return 0;
}

void ListReverse(List* plist)   //反向链表
{
	ListNode* head = plist->_head;
	ListNode* cur = head->_next;
	ListNode* tmp = NULL;
	assert(plist);
	while (cur != plist->_head)
	{
		tmp = cur->_next;
		cur->_next = cur->_prev;
		cur->_prev = tmp;
		cur = cur->_prev;
	}
	tmp = head->_next;
	head->_next = head->_prev;
	head->_prev = tmp;
}
void ListPrint(List* plist)
{
	ListNode* head = plist->_head;
	ListNode* cur = head->_next;
	assert(plist);
	while (cur != head)
	{
		printf("<-%d->", cur->_data);
		cur = cur->_next;
	}
	printf("\n");
}

以上就是关于带头双向循环链表的实现代码，关于无头单向不循环的实习代码可大家可以看我的博客：
链表—单链表