Bidirectional headed circular linked list of linear lists

Ready to work:

Create structure pointer

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

1. Create a new node

Basic idea: malloc node, determine whether the node is created successfully.

LTNode* BuyLTNode(LTDataType x)
{
	LTNode* newnode = (LTNode*)malloc(sizeof(LTNode));//动态开辟节点
	if (newnode == NULL)//判断是否malloc成功
	{
		printf("malloc fail\n");
		exit(-1);//退出程序
	}
	newnode->data = x;//初始化
	newnode->next = NULL;//置空
	newnode->prev = NULL;//置空
	return newnode;
}

2. Tail plug

Basic idea: 1) Create a new node

2) Find the tail node and link it

Drawing:

Code:

void LTNodePushBack(LTNode* phead, LTDataType x)
{
	assert(phead);
	//创建一个新节点
	LTNode* newnode = BuyLTNode(x);
	//链接节点
	LTNode* tail = phead->prev;//找尾节点
	tail->next = newnode;
	newnode->prev = tail;

	newnode->next = phead;
	phead->prev = newnode;
}

3. Head plug

Basic idea: 1) Create a new node

2) Find the first node, link the nodes

Drawing:

Code:

void LTNodePushFront(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* newnode = BuyLTNode(x);
	LTNode* first = phead->next;//找到第一个节点
	//链接
	newnode->next = first;
	first->prev = newnode;

	phead->next = newnode;
	newnode->prev = phead;
}

3. Print the linked list

Basic idea: 1) Assertions

2) Create a cur node, pointing to the first node

3) When cur == phead, the round ends.

Drawing:

Code:

void LTNodePrint(LTNode* phead)
{
	LTNode* cur = phead->next;//一般情况下，不允许动头节点
	while (cur != phead)//当指向phead时，循环结束
	{
		printf("%d ", cur->data);
		cur = cur->next;//更新cur
	}
	printf("\n\n");
}

4. Tail deletion

Basic idea: 1) Assertions

2) Find the tail node and the penultimate node, link phead and tailPrev, free node

Drawing:

Code:

void LTNPopBack(LTNode* phead)
{
	//断言
	assert(phead);
	//找到尾节点和第二个尾节点
	LTNode* tail = phead->prev;
	LTNode* tailPrev = tail->prev;
	//释放尾节点
	free(tail);
	tail = NULL;
	//新的链接
	tailPrev->next = phead;
	phead->prev = tailPrev;

}

 

5. Header deletion

Basic idea: 1) Assertions

2) Find the first and second node, link the phead and the second node, free the first node

Drawing:

Code:

void LTNPopFront(LTNode* phead)
{
	//断言
	assert(phead);
	//找到第一个节点和第二个节点
	LTNode* first = phead->next;
	LTNode* second = first->next;
	//释放内存
	free(first);
	first = NULL;
	//链接
	phead->next = second;
	second->prev = phead;
}

 

6. Find the value of pos

Basic idea: 1) Assertions

2) Traverse the linked list, return the linked list if found, and return NULL if not found

Code:

LTNode* LTNFind(LTNode* phead, LTDataType x)
{
	//断言
	assert(phead);
	//创立一个节点
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		if (cur->data == x)
		{
			//找到返回节点
			return cur;
		}
		cur = cur->next;
	}
	//找不到，返回NULL
	return NULL;
}

7. Insert a new node before pos

Basic idea: 1) Assertions

2) Create a new node and find the node before pos

3) Link newnode pos and previous one of pos

Drawing:

Code:

void LTNInsert(LTNode* pos, LTDataType x)
{
	//断言
	assert(pos);
	//找到pos的前一个节点
	LTNode* prev = pos->prev;
	//创建一个新节点
	LTNode* newnode = BuyLTNode(x);
	
	prev->next = newnode;
	newnode->prev = prev;

	newnode->next = pos;
	pos->prev = newnode;
}

 

8. Delete the pos node

Basic idea: 1) Assertions

2) Create two nodes before and after pos, link, free the pos node

Drawing:

Code:

void LTNErase(LTNode* pos)
{
	//断言
	assert(pos);
	//创建pos对应前后的节点
	LTNode* prev = pos->prev;
	LTNode* next = pos->next;
	//释放节点
	free(pos);
	pos = NULL;
	//链接
	prev->next = next;
	next->prev = prev;
}

9. Destroy the linked list

Basic idea: 1) Assertions

2) Create a cur pointer record

3) One cycle, one node is released one node at a time.

4) phead is finally released and empty.

Code:

void LTNDestroy(LTNode* phead)
{
	//断言
	assert(phead);
	//创建cur指针
	LTNode* cur = phead->prev;
	//循环
	while (cur != phead)
	{
		//记录下一个节点
		LTNode* next = cur->next;
		free(cur);
		//更新
		cur = next;
	}
	//释放并置空
	free(phead);
	phead = NULL;
}

head File:

#include<stdio.h>
#include<assert.h>
#include<stdlib.h>

//双向带头循环链表
typedef int LTDataType;
typedef struct ListNode
{
	LTDataType data;
	struct ListNode* next;
	struct ListNode* prev;
}LTNode;
//尾插
void LTNodePushBack(LTNode* phead, LTDataType x);

LTNode* BuyLTNode(LTDataType x);

void LTNodePrint(LTNode* phead);

LTNode* LTNodeInit();
//头插
void LTNodePushFront(LTNode* phead, LTDataType x);

//尾删
void LTNPopBack(LTNode* phead);

//头删

void LTNPopFront(LTNode* phead);

//查找

LTNode* LTNFind(LTNode* phead, LTDataType x);

//在pos前面插入
void LTNInsert(LTNode* pos, LTDataType x);

//删除pos位置对应的值

void LTNErase(LTNode* pos);

//销毁链表
void LTNDestroy(LTNode* phead);