Circular double linked list tutorial (personal notes)

Circular double linked list tutorial (personal notes)

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foreword

As a C language beginner, I use a blog to store my notes

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1. Define the structure

code show as below:

typedef struct Node//定义结构体
{
    
    
	char date[10]; //数据域 
	struct Node *prior;//指针域 
	struct Node *next;
}Node;

typedef struct Node *PNode;//用来记录首尾的指针 

typedef struct List
{
    
    
	PNode first;//记录表头（头指针） 
	PNode last;//记录最后一个结点（尾指针） 
	int size;//记录结点个数 
}List;

2. Create an empty table

code show as below:

void Creat(List *list)//创造空表 
{
    
    
	Node *s = (Node*)malloc(sizeof(Node));
	list->first = list->last = s;//分别记录头结点的位置
	//创造循环双向空链表 
	list->last->next = list->first;//s->next指向s 
	list->first->prior = list->last;//s->prior指向s 
	list->size = 0;//记录结点个数 
}

3. Insertion method

1. Tail insertion method

code show as below:

void Add(List *list)//尾插法 
{
    
    
	Node *newNode = (Node*)malloc(sizeof(Node));
	printf("请输入你要插入的数据:");
	scanf("%s",newNode->date);
	
	newNode->next = list->first;//新结点尾和表头相接 
	list->first->prior = newNode;//表头指向新结点 
	list->last->next = newNode;//表尾指向新结点 
	newNode->prior = list->last;//新结点的头指向表尾 
	
	list->last = newNode;//尾指针指向新结点（更新表尾为新节点） 
	list->size++;//结点个数增加1 
}

Use the picture below to help me understand better

2. Selection and interpolation

void Insert(List *list)//选插 
{
    
    
	Node *newNode = (Node*)malloc(sizeof(Node));
	int i = 0,j = 0;
	printf("请输入你要插入的数据:");
	scanf("%s",newNode->date);//给新结点数据域赋值 
	printf("请输入%s的插入位置:",newNode->date);
	scanf("%d",&i); 
	
	if(i < 1||i > list->size)
	{
    
    
		printf("该位置不在链表范围内!\n");
		return;
	}
	else
	{
    
    
		Node *p = (Node*)malloc(sizeof(Node));
		p = list->first->next;
		for(j = 1;j < i - 1;j++)
			p = p->next;
		newNode->next = p->next;
		p->next->prior = newNode;
		newNode->prior = p;
		p->next = newNode;
		list->size++;
	}
}

4. Search method

1. Find by location

void Get(List *list)//查找第i个元素
{
    
    
	int i = 0,j = 0;
	printf("请输入你要查找元素的位置:");
	scanf("%d",&i);
	if(i < 1 ||i > list->size)
	{
    
    
		printf("该链表没有第%d个元素\n",i);
		return;
	}
	else
	{
    
    
		Node *p = (Node*)malloc(sizeof(Node));
		p = list->first->next;
		for(j = 1;j < i;j++)
			p = p->next;
		printf("第%d个元素是%s\n",i,p->date);
	}
	
}

2. Search by content

void Locate(List *list)//查找元素e 
{
    
    
	int i = 1;
	char date[10];
	Node *p = (Node*)malloc(sizeof(Node));
	printf("请输入你要查找的数据:");
	scanf("%s",date);
	p = list->first->next;
	for(i = 1;i <= list->size;i++)
	{
    
    
		if(strcmp(p->date,date) == 0)
			break;
		p = p->next;
	}
	if(i > list->size)
	{
    
    
		printf("该链表中没有%s这个元素\n",date);
		return;
	}
	printf("%s是链表的第%d个元素\n",p->date,i);
}

5. Output linked list

void Print(List *list)//输出 
{
    
    
	if(list->size == 0)
	{
    
    
		printf("该表为空表\n");
		return; 
	}
	else
	{
    
    
		int i;
		Node *p = (Node*)malloc(sizeof(Node));
		p = list->first->next; 
		printf("该链表中的元素元素有:\n");
		for(i = 1;i <= list->size;i++)
			{
    
    
				printf("%s  ",p->date);
				p = p->next;
			}
		printf("\n");
	}
}

6. Delete method

1. Delete by location

void Delete(List *list)//选删 
{
    
    
	int i = 0,j = 0;
	Node *p = (Node*)malloc(sizeof(Node));
	p = list->first->next;
	printf("请输入你要删除数据的位置:");
	scanf("%d",&i);
	if(i < 1 || i >list->size)
	{
    
    
		printf("该链表没有第%d个数据,无法删除!\n",i);
		return;	
	}
	else
	{
    
    
		for(j = 1;j < i;j++)
			p = p->next;
		p->next->prior = p->prior;
		p->prior->next = p->next;
		free(p);
		list->size--;
	}
}

2. Delete all

void Destroy(List *list)//全删
{
    
    
	Node *p = (Node*)malloc(sizeof(Node)); 
	Node *q = (Node*)malloc(sizeof(Node));
	p = q = list->first->next;
	for(;list->size > 0;list->size--)
	{
    
    
		p = p->next;
		free(q);
		q = p;
	}
}

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Summarize

The core of the linked list is actually the use of pointers. As a beginner, I can only master it better if I have a solid foundation.