C实现带头双向循环链表

双向循环链表的好处：
可以从任何节点开始，向前或者向后遍历。
可以进行前插也可进行后插。

结构样式：

头文件：

#define _CRT_SECURE_NO_WARNINGS
#include
#include
#include

typedef int LTDataType;

typedef struct ListNode
{
	LTDataType a;
	struct ListNode* prev;   //前指
	struct ListNode* next;   //后指
}ListNode;

//创建返回链表的头节点
ListNode* ListCreat();
//销毁
void ListDestory(ListNode* plist);
//打印
void ListPrint(ListNode* plist);
//尾插
void ListPushBack(ListNode* plist, LTDataType val);
//尾删
void ListPopBack(ListNode* plist);
//创建节点
ListNode* BuyListNode(LTDataType val);
//头插
void ListPushFront(ListNode* plist, LTDataType val);
//头删
void ListPopFront(ListNode* plist);
//查找
LTDataType ListFind(ListNode* head, LTDataType val);
//在pos的位置插入(前插)
void ListInsert(ListNode* pos, LTDataType x, LTDataType val);
//删除pos的节点(前删)
void ListErase(ListNode* pos, LTDataType x);

实现：

#include"LIstNode.h"

//创建返回链表的头节点
ListNode* ListInit()
{
	ListNode* head = (ListNode*)malloc(sizeof(ListNode));
	head->next = head;
	head->prev = head;
	return head;
}
//销毁
void ListDestory(ListNode* head)
{
	assert(head);
	ListNode* cur = head->next;
	while (cur!= NULL || cur->next != NULL)
	{
		ListNode* _next = cur->next;
		free(cur);
		cur = _next;
	}
	free(head);
	head->a = 0;
	head->next = NULL;
	head->prev = NULL;
}
//打印
void ListPrint(ListNode* head)
{
	assert(head);
	ListNode* cur =head->next;
	while (cur != NULL)
	{
		printf("%d ", cur->a);
		cur = cur->next;
	}	
}
//尾插
void ListPushBack(ListNode* head, LTDataType val)
{
	assert(head);
	ListNode* New = BuyListNode(val);
	ListNode* tail = head->prev;
	tail->next = New;
	New->next = head;
	New->prev = tail;
	tail = New;
}
//创建节点
ListNode* BuyListNode(LTDataType val)
{
	ListNode* NewHead = (ListNode*)malloc(sizeof(ListNode));
	NewHead->a = val;
	NewHead->next = NULL;
	NewHead->prev = NULL;
	return NewHead;
}
//尾删
void ListPopBack(ListNode* head)
{
	ListNode* tail = head->prev;
	head->prev = tail->prev;
	tail->prev->next = head;
	tail = head->prev;
}
//头插
void ListPushFront(ListNode* head, LTDataType val)
{
	ListNode* cur = head->next;
	ListNode* New = BuyListNode(val);
	head->next = New;
	New->prev = head;
	New->next = cur;
	cur->prev = New;
}
//头删
void ListPopFront(ListNode* head)
{
	ListNode* cur = head->next;
	ListNode* _next = cur->next;
	head->next = _next;
	_next->prev = head;
}
//查找
LTDataType ListFind(ListNode* head, LTDataType val)
{
	ListNode* cur = head->next;
	int count = 1;
	while (cur != NULL)
	{
		if (cur->a == val)
			return count;
		cur = cur->next;
		++count;
	}
	return -1;
}

//在pos的位置插入(前插)
void ListInsert(ListNode* pos, LTDataType x, LTDataType val)
{
	ListNode* New = BuyListNode(val);
	int count = 1;
	ListNode* cur = pos->next;
	while (count < x)
	{
		cur = cur->next;
		++count;
	}
	New->prev = cur->prev;
	cur->prev->next = New;
	New->next = cur;
	cur->prev = New;
}
//删除pos的节点(前删)
void ListErase(ListNode* pos, LTDataType x)
{
	int count = 1;
	ListNode* cur = pos->next;
	while (count < x)
	{
		cur = cur->next;
		++count;
	}
	cur->prev = cur->prev->prev;
	cur->prev->next = cur;
}