【数据结构】——带头双向循环链表

目录

1.带头双向循环链表

2.链表实现

2.1可完成带头双向可循环链表节点的结构体

2.2申请一个可双向循环的节点

2.3初始化链表

2.4尾插

2.5尾删

2.6头插

2.7头删

2.8打印

2.9查找（修改）

2.10在pos之前插入x

2.11删除pos位置

 2.12判空

2.13记录链表大小

2.14销毁

3.完整的带头双向循环链表代码

3.1——List.h

3.2——List.c

---

1.带头双向循环链表

对比：

我们实际中最常用还是 两种 链表结构：

1.无头单向非循环链表

用处： 

结构简单 ，一般不会单独用来存数据。实际中更多是作为 其他数据结 构的子结构 ，

如哈希桶、图的邻接表等等。另外这种结构在 笔试面试 中出现很多。

2.带头双向循环链表

 用处：

结构在链表中最复杂 ，一般用在单独存储数据。实际中使用的链表数据结构，都是带头双向循环链表。另外这个结构虽然结构复杂，但是使用代码实现以后会发现结构会带来很多优势，反而使得实现功能更简单了。

2.链表实现

2.1可完成带头双向可循环链表节点的结构体

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

2.2申请一个可双向循环的节点

LTNode* BuyListNode(LTDataType x)
{
	LTNode* node = (LTNode*)malloc(sizeof(LTNode));
	if (node == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}

	node->data = x;
	node->next = NULL;
	node->prev = NULL;
	return node;
}

2.3初始化链表

LTNode* ListInit()
{
	LTNode* phead = BuyListNode(-1);
	phead->next = phead;
	phead->prev = phead;

	return phead;
}

2.4尾插

void LTPushBack(LTNode* phead, LTDataType x)
{
	assert(phead);

	//方法1
	/*LTNode* newnode = BuyListNode(x);
	LTNode* tail = phead->prev;

	tail->next = newnode;
	newnode->prev = tail;

	newnode->next = phead;
	phead->prev = newnode;*/
	
	//方法2
	LTInsert(phead, x);
}

2.5尾删

void LTPopBack(LTNode* phead)
{
	assert(phead);
	assert(phead->next != phead);  // 空

	//方法1
	//LTNode* tail = phead->prev;
	//LTNode* tailPrev = tail->prev;

	//tailPrev->next = phead;
	//phead->prev = tailPrev;
	//free(tail);

	//方法2
	LTErase(phead->prev);
}

2.6头插

void LTPushFront(LTNode* phead, LTDataType x)
{
	assert(phead);
	
	//方法1（有关顺序）
	/*LTNode* newnode = BuyListNode(x);
	newnode->next = phead->next;
	phead->next->prev = newnode;

	phead->next = newnode;
	newnode->prev = phead;*/

	//方法2（无关顺序）
	//LTNode* newnode = BuyListNode(x);
	//LTNode* first = phead->next;

	 phead newnode first 
	 顺序无关
	//phead->next = newnode;
	//newnode->prev = phead;
	//newnode->next = first;
	//first->prev = newnode;

	//方法3
	LTInsert(phead->next, x);

}

2.7头删

void LTPopFront(LTNode* phead)
{
	assert(phead);
	assert(phead->next != phead); // 空

	//方法1
	/*LTNode* first = phead->next;
	LTNode* second = first->next;

	free(first);

	phead->next = second;
	second->prev = phead;*/
	
	//方法2
	LTErase(phead->next);
}

2.8打印

void LTPrint(LTNode* phead)
{
	assert(phead);

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

2.9查找（修改）

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;
}

2.10在pos之前插入x

 

// 在pos之前插入x
void LTInsert(LTNode* pos, LTDataType x)
{
	assert(pos);

	LTNode* prev = pos->prev;
	LTNode* newnode = BuyListNode(x);
	// prev newnode pos
	prev->next = newnode;
	newnode->prev = prev;
	newnode->next = pos;
	pos->prev = newnode;
}

2.11删除pos位置

// 删除pos位置
void LTErase(LTNode* pos)
{
	assert(pos);

	LTNode* prev = pos->prev;
	LTNode* next = pos->next;
	free(pos);

	prev->next = next;
	next->prev = prev;
}

 2.12判空

bool LTEmpty(LTNode* phead)
{
	assert(phead);

	/*if (phead->next == phead)
	{
		return true;
	}
	else
	{
		return false;
	}*/

	return phead->next == phead;
}

2.13记录链表大小

size_t LTSize(LTNode* phead)
{
	assert(phead);

	size_t size = 0;
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		++size;
		cur = cur->next;
	}

	return size;
}

2.14销毁

void LTDestroy(LTNode* phead)
{
	assert(phead);

	LTNode* cur = phead->next;
	while (cur != phead)
	{
		LTNode* next = cur->next;
		free(cur);      

		cur = next;
	}

	free(phead);
	//phead = NULL;
}

3.完整的带头双向循环链表代码

3.1——List.h

#pragma once

#include 
#include 
#include 
#include 

//typedef char LTDataType;
//typedef double LTDataType;
typedef int LTDataType;

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

//创建节点
LTNode* BuyListNode(LTDataType x);
//初始化
LTNode* LTInit();

//打印
void LTPrint(LTNode* phead);
//尾插尾删
void LTPushBack(LTNode* phead, LTDataType x);
void LTPopBack(LTNode* phead);
//头插头删
void LTPushFront(LTNode* phead, LTDataType x);
void LTPopFront(LTNode* phead);
//查找
LTNode* LTFind(LTNode* phead, LTDataType x);

// pos前面插入
void LTInsert(LTNode* pos, LTDataType x);
// pos位置删除
void LTErase(LTNode* pos);
//判空
bool LTEmpty(LTNode* phead);
//大小
size_t LTSize(LTNode* phead);
//销毁
void LTDestroy(LTNode* phead);

3.2——List.c

#include "List.h"

LTNode* BuyListNode(LTDataType x)
{
	LTNode* node = (LTNode*)malloc(sizeof(LTNode));
	if (node == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}

	node->data = x;
	node->next = NULL;
	node->prev = NULL;
	return node;
}

LTNode* LTInit()
{
	LTNode* phead = BuyListNode(-1);
	phead->next = phead;
	phead->prev = phead;

	return phead;
}

void LTPrint(LTNode* phead)
{
	assert(phead);

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

void LTPushBack(LTNode* phead, LTDataType x)
{
	assert(phead);

	//方法1
	/*LTNode* newnode = BuyListNode(x);
	LTNode* tail = phead->prev;

	tail->next = newnode;
	newnode->prev = tail;

	newnode->next = phead;
	phead->prev = newnode;*/
	
	//方法2
	LTInsert(phead, x);
}

void LTPopBack(LTNode* phead)
{
	assert(phead);
	assert(phead->next != phead);  // 空

	//方法1
	//LTNode* tail = phead->prev;
	//LTNode* tailPrev = tail->prev;

	//tailPrev->next = phead;
	//phead->prev = tailPrev;
	//free(tail);

	//方法2
	LTErase(phead->prev);
}

void LTPushFront(LTNode* phead, LTDataType x)
{
	assert(phead);
	
	//方法1（有关顺序）
	/*LTNode* newnode = BuyListNode(x);
	newnode->next = phead->next;
	phead->next->prev = newnode;

	phead->next = newnode;
	newnode->prev = phead;*/

	//方法2（无关顺序）
	//LTNode* newnode = BuyListNode(x);
	//LTNode* first = phead->next;

	 phead newnode first 
	 顺序无关
	//phead->next = newnode;
	//newnode->prev = phead;
	//newnode->next = first;
	//first->prev = newnode;

	//方法3
	LTInsert(phead->next, x);

}

void LTPopFront(LTNode* phead)
{
	assert(phead);
	assert(phead->next != phead); // 空

	//方法1
	/*LTNode* first = phead->next;
	LTNode* second = first->next;

	free(first);

	phead->next = second;
	second->prev = phead;*/
	
	//方法2
	LTErase(phead->next);
}

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;
}

// 在pos之前插入x
void LTInsert(LTNode* pos, LTDataType x)
{
	assert(pos);

	LTNode* prev = pos->prev;
	LTNode* newnode = BuyListNode(x);
	// prev newnode pos
	prev->next = newnode;
	newnode->prev = prev;
	newnode->next = pos;
	pos->prev = newnode;
}

// 删除pos位置
void LTErase(LTNode* pos)
{
	assert(pos);

	LTNode* prev = pos->prev;
	LTNode* next = pos->next;
	free(pos);

	prev->next = next;
	next->prev = prev;
}

//判空
bool LTEmpty(LTNode* phead)
{
	assert(phead);

	/*if (phead->next == phead)
	{
		return true;
	}
	else
	{
		return false;
	}*/

	return phead->next == phead;
}

size_t LTSize(LTNode* phead)
{
	assert(phead);

	size_t size = 0;
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		++size;
		cur = cur->next;
	}

	return size;
}

void LTDestroy(LTNode* phead)
{
	assert(phead);

	LTNode* cur = phead->next;
	while (cur != phead)
	{
		LTNode* next = cur->next;
		free(cur);      

		cur = next;
	}

	free(phead);
	//phead = NULL;
}