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前言

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📋专栏：数据结构
🔑本章内容：[数据结构]—链表之带头双向循环链表
送给各位💌：不谈以前不说如果只希望未来越来越好
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提示：以下是本篇文章正文内容，下面案例可供参考

🌟一、带头双向循环链表

🌏1.1头删：

💫1.1.1代码：

void LTPopFront(LTNode* phead)
{
	assert(phead);
	LTNode* cur = phead->next;
	phead->next = cur->next ;
	cur->next->prev = phead;
	free(cur);
}

💫1.1.2流程图：

定义一个指针时：(代码如上图)

定义两个指针时：(建议使用两个—代码如下图)

🌏1.2尾删：

💫1.2.1代码：

void LTPopBack(LTNode* phead)
{
	assert(phead);
	assert(!LTEmpty(phead));
	LTNode* tail = phead->prev;
	LTNode* tailPrev = tail->prev;
	free(tail);
	phead->prev = tailPrev;
	tailPrev->next = phead;
}

💫1.2.2流程图：

第一种：

第二种：

第三种：需要注意

🌏1.3查找：

LTNode* LTFind(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		if (cur->data == x)
		{
			return cur;
		}
		cur = cur->next;
	}
	return NULL;
}

🌏1.4在pos位置之前插入：

💫1.4.1代码：

void LTInsert(LTNode* pos, LTDataType x)
{
	assert(pos);
	LTNode* newnode = BuyLTNode(x);
	pos->prev->next  = newnode;
	newnode->prev = pos->prev;
	newnode->next = pos;
	pos->prev = newnode;
	
	//第二种：
	///LTNode* prev = pos->prev;
	//prev->next = newnode;
	//newnode->prev = prev;
	//pos->prev = newnode;
	//newnode->next = pos;
}

💫1.4.2流程图：

第一种：

第二种：

🌏1.5在pos位置删除：

💫1.5.1代码：

void LTErase(LTNode* pos)//要注意不能传哨兵位
{
	assert(pos);
	LTNode* posPrev = pos->prev;
	LTNode* posNext = pos->next;
	posPrev->next = posNext;
	posNext->prev = posPrev;
	free(pos);
}

💫1.5.2代码：

🌏1.6释放链表：

void LTDestroy(LTNode* phead)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		LTNode* next = cur->next;
		free(cur);
		cur = next;
	}
	free(phead);
}

🌟二、完整带头双向循环链表

//List.h
#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
#include<stdbool.h>

typedef int LTDataType;
typedef struct ListNode
{
	struct ListNode* next;
	struct ListNode* prev;
	LTDataType data;
}LTNode;

LTNode* LTInit();
void LTNodePrint(LTNode* phead);
bool LTEmpty(LTNode* phead);
void LTPushFront(LTNode* phead, LTDataType x);
void LTPushBack(LTNode* phead, LTDataType x);
void LTPopFront(LTNode* phead);
void LTPopBack(LTNode* phead);
LTNode* LTFind(LTNode* phead, LTDataType x);
//在pos之前插入
void LTInsert(LTNode* pos, LTDataType x);
//删除pos位置的值
void LTErase(LTNode* pos);
void LTDestroy(LTNode* phead);

//List.c
#define _CRT_SECURE_NO_WARNINGS 1
#include"List.h"
bool LTEmpty(LTNode* phead)
{
	assert(phead);
	return phead->next == phead;
}
LTNode* BuyLTNode(LTDataType x)
{
	LTNode* newnode = (LTNode*)malloc(sizeof(LTNode));
	if (newnode == NULL)
	{
		perror("malloc fail");
	}
	newnode->data = x;
	newnode->next = NULL;
	newnode->prev = NULL;
	return newnode;
}
LTNode* LTInit()
{
	LTNode* phead = BuyLTNode(-1);
	phead->next = phead;
	phead->prev = phead;
	return phead;
}

void LTNodePrint(LTNode* phead)
{
	assert(phead);
	LTNode* cur = phead->next;
	printf("guard<==>");
	while (cur != phead)
	{
		printf("%d<==>", cur->data);
		cur = cur->next;
	}
	printf("\n");
}

void LTPushFront(LTNode* phead, LTDataType x)
{
	LTNode* newnode = BuyLTNode(x);
	LTNode* cur = phead->next;
	newnode->prev = phead;
	phead->next = newnode;
	newnode->next = cur;
	cur->prev = newnode;
}

void LTPushBack(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* newnode = BuyLTNode(x);
	LTNode* tail = phead->prev;
	tail->next = newnode;
	newnode->prev = tail;
	newnode->next = phead;
	phead->prev = newnode;
}

void LTPopFront(LTNode* phead)
{
	assert(phead);
	LTNode* cur = phead->next;
	//LTNode* next = cur->next;
	phead->next = cur->next ;
	cur->next->prev = phead;
	free(cur);
}

void LTPopBack(LTNode* phead)
{
	assert(phead);
	assert(!LTEmpty(phead));
	LTNode* tail = phead->prev;
	LTNode* tailPrev = tail->prev;
	free(tail);
	phead->prev = tailPrev;
	tailPrev->next = phead;
}

LTNode* LTFind(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		if (cur->data == x)
		{
			return cur;
		}
		cur = cur->next;
	}
	return NULL;
}

void LTInsert(LTNode* pos, LTDataType x)
{
	assert(pos);
	LTNode* newnode = BuyLTNode(x);
	pos->prev->next  = newnode;
	newnode->prev = pos->prev;
	newnode->next = pos;
	pos->prev = newnode;
	//第二种：
	///LTNode* prev = pos->prev;
	//prev->next = newnode;
	//newnode->prev = prev;
	//pos->prev = newnode;
	//newnode->next = pos;
}

void LTErase(LTNode* pos)//要注意不能传哨兵位
{
	assert(pos);
	LTNode* posPrev = pos->prev;
	LTNode* posNext = pos->next;
	posPrev->next = posNext;
	posNext->prev = posPrev;
	free(pos);
}
void LTDestroy(LTNode* phead)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		LTNode* next = cur->next;
		free(cur);
		cur = next;
	}
	free(phead);
}

//Test.c
#define _CRT_SECURE_NO_WARNINGS 1
#include"List.h"
void TestList()
{
	LTNode* plist = LTInit();
	LTPushBack(plist, 1);
	LTPushBack(plist, 2);
	LTPushBack(plist, 3);
	LTPushBack(plist, 4);
	LTNodePrint(plist);
	//LTPushFront(plist, 1);
	//LTPushFront(plist, 2);
	//LTPushFront(plist, 3);
	//LTPushFront(plist, 4);
	//LTNodePrint(plist);
	/*LTPopBack(plist);
	LTNodePrint(plist);*/
	/*LTPopFront(plist);
	LTNodePrint(plist);*/
	/*LTNode* pos = LTFind(plist,3);
	if (pos)
	{
		LTInsert(pos, 30);
	}
	LTNodePrint(plist);*/
	LTNode* pos = LTFind(plist, 2);
	if (pos)
	{
		LTErase(pos, 30);
	}
	LTNodePrint(plist);
	LTDestroy(plist);
	plist = NULL;
}
int main()
{
	TestList();
	return 0;
}

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😽总结

😽Ending,今天的链表之带头双向循环链表(中)的内容就到此结束啦~，如果后续想了解更多，就请关注我吧，一键三连哦 ~