目录

0.结构体定义

1.初始化

2.尾插

3.打印

4.头插

5.任意位置插入前面位置

6.尾删

7.头删

8.链表长度

9.任意位置删除当前位置

10. 销毁

---

 

 

双向带头循环链表：结构复杂，操作简单

0.结构体定义

这里方便浏览，特地没有将int类型重命名为TLDateType 

#define _CRT_SECURE_NO_WARNINGS 1
#pragma once
#include
#include
#include
#include
 
struct ListNode
{
	int val;
	struct ListNode* prev;
	struct ListNode* next;
};

1.初始化

1. 带头需要初始化一个哨兵位头结点
2. 传二级指针
3. 初始化自己的prev和next都指向自己

void ListInit(struct ListNode** pphead)
{
	struct ListNode* Guard = (struct ListNode*)malloc(sizeof(struct ListNode));
	if (Guard == NULL)
	{
		perror("ListInit");
		return;
	}
	*pphead = Guard;
	Guard->next = Guard;
	Guard->prev = Guard;
}

2.尾插

1. 一级指针
2. 直接prev找尾
3. 即是无首元结点，也可（头结点自环）

struct ListNode* BuyListNode(int x)
{
	struct ListNode* newnode = (struct ListNode*)malloc(sizeof(struct ListNode));
	if (newnode == NULL)
	{
		perror("BuySListNode");
		return NULL;
	}
	newnode->val = x;
	newnode->prev = NULL;
	newnode->next = NULL;
	return newnode;
}
 
void ListPushBack(struct ListNode* phead,int x)
{
	assert(phead);
	struct ListNode* newnode = BuyListNode(x);
 
	struct ListNode* tail = phead->prev;
 
	newnode->next = phead;
	phead->prev = newnode;
 
	tail->next = newnode;
	newnode->prev = tail;
}

3.打印

1. 可assert断言（建议单链表不用断言）---头结点
2. 起始条件cur=phead->next;
3. 循环终止条件cur==phead

void ListPrint(struct ListNode* phead)
{
	assert(phead);
	struct ListNode* cur = phead->next;
	while (cur != phead)
	{
		printf("%d->", cur->val);
		cur = cur->next;
	}
	printf("NULL\n");
}

4.头插

1. 一级指针
2. 即是无首元结点，也可（头结点自环）

void ListPushFront(struct ListNode* phead,int x)
{
	assert(phead);
	struct ListNode* newnode = BuyListNode(x);
 
	struct ListNode* next = phead->next;
 
	newnode->next = next;
	next->prev = newnode;
 
	phead->next = newnode;
	newnode->prev = phead;
 
}

5.任意位置插入前面位置

1. 因为有prev，前插不同phead
2. 尾插,头插就用ListInsert传不同pos参数
3. 如果pos传phead,就相当于于是尾插
4. 如果pos传phead->next，就相当于于是头插

void ListInsert(struct ListNode* pos, int x)
{
	assert(pos);
	struct ListNode* newnode = BuyListNode(x);
	struct ListNode* prev = pos->prev;
 
	prev->next = newnode;
	newnode->prev = prev;
 
	newnode->next = pos;
	pos->prev = newnode;
}
 
头插：ListNode(phead->next,x);
尾插:ListNode(phead,x);

6.尾删

1. 不为空，!ListEmpty(plhead)
2. prev,tail,phead

bool ListEmpty(struct ListNode* phead)
{
	return phead->next == phead;
}
 
void ListPopBack(struct ListNode* phead)
{
	assert(phead);
	assert(!ListEmpty(phead));
	struct ListNode* tail = phead->prev;
	struct ListNode* prev = tail->prev;
	
	prev->next = phead;
	phead->prev = prev;
	free(tail);
	tail = NULL;
}

7.头删

1. 不为空，!ListEmpty(plhead)
2. phead,first,second

void ListPopFront(struct ListNode* phead)
{
	assert(phead);
	assert(!ListEmpty(phead));
 
	struct ListNode* first = phead->next;
	struct ListNode* second = first->next;
 
	phead->next = second;
	second->prev = phead;
	free(first);
	first = NULL;
}

8.链表长度

1. 起始条件:cur=phead->next
2. 终止条件:cur!=phead;

size_t ListSize(struct ListNode* phead)
{
	size_t size = 0;
	struct ListNode* cur = phead->next;
	while (cur != phead)
	{
		++size;
		cur = cur->next;
	}
	return size;
}

9.任意位置删除当前位置

1. 不为空，!ListEmpty(plhead)
2. 尾删，头删就用ListErase传不同pos参数
3. 如果pos传phead->prev，就是尾删
4. 如果pos传phead->next,就是头删

void ListErase(struct ListNode* pos)
{
	assert(pos);
	struct ListNode* prev = pos->prev;
	struct ListNode* next = pos->next;
 
	prev->next = next;
	next->prev = prev;
 
	free(pos);
	pos = NULL;
}

10. 销毁

1. 看是否保留哨兵头，来传一级或二级指针
2. 先保留哨兵头作为判断循环条件，最后决定是否释放哨兵头

void ListDestory(struct ListNode** pphead)
{
	assert(pphead);
	struct ListNode* cur = (*pphead)->next;
	while (cur != *pphead)
	{
		struct ListNode* next = cur->next;
		free(cur);
		cur = next;
	}
	free(*pphead);
	*pphead = NULL;
}

制作不易，敬请三连