循环链表是另一种形式的链式存贮结构。它的特点是表中最后一个结点的指针域指向头结点，整个链表形成一个环。

//节点
struct node{
  int data1;
  node *next;
}; 


//链表类 头部文件
class singlelink{
  private:
    node data;
    int length;
  public:
    singlelink(){
      length=0;
      data.data1=0;
      data.next=&data;
    }
    ~singlelink(){};
    bool isempty(){
      if(length==0)
        return true;
      else 
       	return false;
    }
    int returnlength(){
      return length;
    }
    bool insert(int position, int num);
    bool deletenode(int position);
    int returnnum(int position);
    void returnallnum(int position);
    bool deleteall();
    void headinsert(int num);
    void rearinsert(int num);
    
};


//方法
bool singlelink::insert(int position, int num){
    if(position>length+1)
      return false;
    else{
      node* probe=&data;
      for(int i=1;i<position;i++){
        probe=probe->next;
      }
      node* newnode=new node;
      newnode->data1=num;
      newnode->next=probe->next;
      probe->next=newnode;
      length++;
    }
    return true;
  }
  bool  singlelink::deletenode(int position){
    if(position>length)
      return false;
    else{
      node* probe=&data;
      node* temp=NULL;
      for(int i=1;i<position;i++){
        probe=probe->next;
      }
      temp=probe->next;
      probe->next=probe->next->next; 
      free(temp);
      length--;
      return true;
      
    }	
  }
  int singlelink::returnnum(int position){
    node* probe=&data;
    for(int i=1;i<=position;i++){
      probe=probe->next;
    }
    return probe->data1;
  }
  bool singlelink::deleteall(){
    node* probehead=&data;
    node* proberear=NULL;
    while(probehead->next!=&data){
      proberear=probehead->next;
      free(probehead);
      probehead=proberear;
      length--;
    }
    free(probehead);
    if(length==0)
      return true;
    else
      return false;
  }
  void singlelink::headinsert(int num){
    node* probe=&data;
    node* newnode=new node;
    newnode->data1=num;
    newnode->next=probe->next;
    probe->next=newnode;
    length++;
  }
  void singlelink::rearinsert(int num){
    node* probe=&data;
    for(int i=1;i<=length;i++){
      probe=probe->next;
    }
    node* newnode=new node;
    newnode->data1=num;
    newnode->next=&data;
    probe->next=newnode;
    length++;
  }
  void singlelink::returnallnum(int position){
    int times=0;
    node* probe=&data;
    for(int i=1;i<=position;i++){
      probe=probe->next;
    }
    while(times<length){
      if(probe!=(&data)){
      
      cout<<probe->data1<<" ";
      times++;
      probe=probe->next;
    }
      else
      probe=probe->next;
    } 
  }


//主函数
int main(){
    singlelink a1,a2;
    if(a1.isempty())
    cout<<"是空链表"<<endl;
    for(int i=1, j=10;i<21;i++,j++){
      a1.headinsert(j);
      a2.rearinsert(j);
    }
    cout<<"a1，a2的长度分别是"<<a1.returnlength()<<"  "<<a2.returnlength()<<endl;
    cout<<"a1成员为"<<endl; 
    for (int i=1;i<=a1.returnlength();i++){
    cout<<a1.returnnum(i)<<" ";
    }
    cout<<endl;
    cout<<"a2成员为"<<endl; 
    for (int i=1;i<=a2.returnlength();i++){
    cout<<a2.returnnum(i)	<<" ";
    }
    cout<<endl;
    a1.deletenode(9);
    cout<<"删除第9node后a1成员为"<<endl; 
    for (int i=1;i<=a1.returnlength();i++){
    cout<<a1.returnnum(i)	<<" ";
    }
    cout<<endl;
    a1.insert(9,520);
    cout<<"插入第9node后a1成员为"<<endl; 
    for (int i=1;i<=a1.returnlength();i++){
    cout<<a1.returnnum(i)	<<" ";
    }
    cout<<endl;
    a1.returnallnum(9);
    cout<<endl;
    if(a1.deleteall())
    cout<<"删除a1成功"<<endl;
    return 0;
  }