所实现的循环单链表的结构例如以下图所看到的：

循环单链表的实现，和上一篇文章单链表的实现大致同样点击打开链接，略有差别：

1：循环推断的条件不再是s == NULL或者s->next == NULL,而是他们是否等于头指针。2: 断开链表时的处理，尾节点的next不是NULL，而是指向头结点

详细细节參考上一篇文章

头文件：SCList.h

#ifndef SCLIST_H
#define SCLIST_H#include<iostream>
#include<cassert>
using namespace std;typedef enum{ FALSE, TRUE }Status;template<class Type>
class List;template<class Type>
class ListNode
{friend class List<Type>;
private:Type data;ListNode *next;
public:ListNode() :data(Type()), next(NULL){}ListNode(Type d, ListNode<Type> *n = NULL) :data(d), next(n){}void SetData(Type d){ data = d; }Type GetData()const{ return data; }~ListNode(){}
};template<class Type>
class List
{
private:ListNode<Type> *first;ListNode<Type> *last;size_t         size;
public:List(){ListNode<Type> *s = new ListNode<Type>;assert(s != NULL);first = last = s;last->next = first;}~List(){destory();}Status push_back(const Type &x){ListNode<Type> *s = new ListNode<Type>(x);if (s == NULL)return FALSE;last->next = s;last = s;last->next = first;size++;return TRUE;}void show_list(){ListNode<Type> *s = first->next;while (s != first){cout << s->data << "->";s = s->next;}cout << "Nul." << endl;}Status push_front(const Type &x){ListNode<Type> *s = new ListNode<Type>(x);if (s == NULL)return FALSE;s->next = first->next;first->next = s;if (size == 0){last = s;last->next = first;//---------------->能够省略，think}size++;return TRUE;}Status pop_back(){if (size == 0)//{cout << "循环单链表已空，无法尾删" << endl;return FALSE;}ListNode<Type> *s = first;while (s->next != last)s = s->next;delete last;last = s;last->next = first;size--;return TRUE;}Status pop_front(){if (size == 0)//{cout << "循环单链表已空。无法头删" << endl;return FALSE;}ListNode<Type> *s = first->next;first->next = s->next;delete s;if (size == 1){last = first;last->next = first;//能够省略-------------->}size--;return TRUE;}Status insert_val(const Type &x){ListNode<Type> *s = first;while (s->next != first && s->next->data < x)s = s->next;if (s->next == first)push_back(x);else{ListNode<Type> *p = new ListNode<Type>(x);assert(p != NULL);p->next = s->next;s->next = p;size++;}return TRUE;}ListNode<Type>* find(const Type &x){if (size == 0)return NULL;ListNode<Type> *s = first->next;while (s != first){if (s->data == x)return s;s = s->next;}return NULL;}Status delete_val(const Type &x){ListNode<Type> *s = find(x);if (s == NULL){cout << "该元素不存在，无法删除" << endl;return FALSE;}if (s == last){pop_back();}else{ListNode<Type> *p = s->next;s->data = p->data;s->next = p->next;if (p == last)//------------------->>注意{last = s;}delete p;size--;}return TRUE;}//从第一个节点处断开，一分为二，头结点和第一个节点成为一个单独的循环单链表//将剩余的节点依次按值插入该链表void sort(){if (size == 0 || size == 1)return;ListNode<Type> *s = first->next;ListNode<Type> *p = s->next;last = s;  last->next = first;while (p != first){s = p;p = p->next;//insert_val(s->data);//delete s;ListNode<Type> *q = first;while (q->next != NULL && q->next->data < s->data){q = q->next;}if (q->next == NULL){last->next = s;last = s;last->next = first;}else{s->next = q->next;q->next = s;}}}//从第一个节点处断开，一分为二，头结点和第一个节点成为一个单独的循环单链表//将剩余的节点依次进行头插void reserve(){if (size == 0 || size == 1)return;ListNode<Type> *s = first->next;ListNode<Type> *p = s->next;last = s;last->next = first;while (p != first){s = p;p = p->next;s->next = first->next;first->next = s;}}size_t lenth(){return size;}void clear(){if (size == 0)return;ListNode<Type> *s = first->next;while (s != first){if (size == 1){last = first;last->next = first;}else{first->next = s->next;}delete s;size--;s = first->next;}}ListNode<Type>* next(ListNode<Type> *s){if (s == last)//最后一个节点没有后继return NULL;elsereturn s->next;}ListNode<Type>* prio(ListNode<Type> *s){if (s == first->next)//第一个节点没有前驱return NULL;ListNode<Type> *p = first;while (p->next != s){p = p->next;}return p;}void destory(){clear();delete first;first = last = NULL;}
};
#endif

測试文件：main.cpp

#include"SCList.h"int main()
{List<int> mylist;int item;int n;int select = 1;//ListNode<int> *p;while (select){cout << "*************************************** *" << endl;cout << "*[1] push_back           [2] push_front *" << endl;cout << "*[3] show_list           [4] pop_back   *" << endl;cout << "*[5] pop_front           [6] insert_val *" << endl;cout << "*[7] lenth               [8] find       *" << endl;cout << "*[9] merge               [10] delete_val*" << endl;cout << "*[11] sort               [12] reserve   *" << endl;cout << "*[13] next               [14] clear     *" << endl;cout << "*[15] prio               [0] quit_system*" << endl;cout << "请选择：>";cin >> select;switch (select){case 1:cout << "请输入要插入的元素（-1结束):>";while (cin >> item, item != -1){mylist.push_back(item);}break;case 2:cout << "请输入要插入的元素（-1结束）:>";while (cin >> item, item != -1){mylist.push_front(item);}break;case 3:mylist.show_list();break;case 4:mylist.pop_back();break;case 5:mylist.pop_front();break;case 6:cout << "请输入要插入的元素：";cin >> item;mylist.insert_val(item);break;case 7:cout << "长度为：" << mylist.lenth() << endl;break;case 8:cout << "请输入要查找的元素：";cin >> item;if (mylist.find(item))cout << "it's found" << endl;elsecout << "it's not exist" << endl;break;case 9:cout << "请输入要删除的位置：";cin >> n;//mylist.delete_pos(n,item);break;case 10:cout << "请输入要删除的元素：";cin >> item;mylist.delete_val(item);break;case 11:mylist.sort();break;case 12:mylist.reserve();break;case 13:cout << "请输入要查找后继的元素：";cin >> item;//p = mylist.next(item);//if (p != NULL)//  cout << p->GetData() << endl;break;case 14:mylist.clear();break;default:break;}}system("pause");return 0;
}