/************************************************************************//* @author lynnbest双向循环列表的使用：1.创建2.插入3.删除4.打印5.按位置查找6.按内容查找7.退出                                                                *//************************************************************************/#include 
    
     #include 
     
      typedef struct node{	int data;	struct node *prior;	struct node *next;}Dlistnode;Dlistnode *CreateDClist(int n);void printflist(Dlistnode *head);int lengthlist(Dlistnode *head);void InsertDClist(Dlistnode *head,int pos);void DeleteDClist(Dlistnode *head,int pos);void main(){	printf("   双向循环链表基本操作	\n");	printf("----by lynnbest ----\n\n");	int  choice,num;	Dlistnode *head;	while(1)	{		printf("1---创建一个双向循环链表\n");		printf("2---插入节点操作\n");		printf("3---删除节点操作\n");		printf("4---打印链表元素\n");		printf("5---查找操作(按位置)\n");		printf("6---查找操作(按内容)\n");		printf("7---退出\n请输入操作：\n");		scanf("%d",&choice);		switch(choice)		{			case 1:					printf("请输入创建元素的个数:\n");					scanf("%d",&num);					head=CreateDClist(num);					break;			case 2:						printf("输入插入的位置:\n");					scanf("%d",&num);					InsertDClist(head,num);					break;			case 3:					printf("输入删除的位置:\n");					scanf("%d",&num);					DeleteDClist(head,num);					break;			case 4:				printflist(head);			//	printf("共有%d个元素\n",lengthlist(head));				break;			case 5:				break;			case 6:				break;			case 7:				return ;				break;			default :				break;		}			}}Dlistnode *CreateDClist(int n) //创建一个带头节点的双向循环链表{	Dlistnode *head,*newnode,*pre;	int data;	if(NULL==(head=(Dlistnode *)malloc(sizeof(Dlistnode))))	{		printf("头结点创建失败\n");		exit(-1);	}	pre=head;	for(int i=1;i<=n;i++)	{		if(NULL==(newnode=(Dlistnode *)malloc(sizeof(Dlistnode))))		{			printf("创建失败\n");			exit(-1);		}		printf("请输入第%d个元素\n",i);		scanf("%d",&data);		newnode->data=data;		//开始插入		pre->next=newnode;			newnode->prior=pre;		pre=newnode;		newnode->next=NULL;	}	newnode->next=head;	head->prior=newnode;	//做首位循环	return head;}void printflist(Dlistnode *head){	Dlistnode *cur=head->next;	while(cur->next!=head)	{		printf("%3d",cur->data);		cur=cur->next;	}	printf("%3d\n",cur->data);		return ;}int lengthlist(Dlistnode *head){	Dlistnode *cur=head;	int count=0;	while(cur->next!=head)	{			count++;		cur=cur->next;	}	return count;}void InsertDClist(Dlistnode *head,int pos){		if(pos<1||pos>lengthlist(head)+1){		printf("插入位置非法\n");		return ;	}	Dlistnode *cur=head,*newnode;	int data;	//完成插入点数据建立	if(NULL==(newnode=(Dlistnode *)malloc(sizeof(Dlistnode))))	{		printf("创建失败\n");		exit(-1);	}	printf("请输入要插入的节点数据:\n");	scanf("%d",&data);	newnode->data=data;	for(int i=0;i
      
       next;	//开始插入	cur->prior->next=newnode;	//插入需要4步	newnode->prior=cur->prior;	newnode->next=cur;	cur->prior=newnode;}void DeleteDClist(Dlistnode *head,int pos){	if(pos<1||pos>lengthlist(head)){		printf("删除位置非法\n");		return ;	}	Dlistnode *cur=head;	for(int i=0;i
       
        next;	//删除 需要3步	cur->prior->next=cur->next;	//前一个指针指向删除节点的下一个	cur->next->prior=cur->prior;//删除节点的前驱指针 指向删除节点前一个节点	free(cur);//释放堆}