C语言版本：循环单链表的实现

SClist.h

 #ifndef __SCLIST_H__
 #define __SCLIST_H__

 #include<cstdio>
 #include<malloc.h>
 #include<assert.h>
 typedef int ElemType;
 typedef struct Node {
     ElemType data;
     struct Node *next;
 }Node,*PNode;

 typedef struct List {
     PNode first;
     PNode last;
     size_t size;
 }List;

 void InitSClist(List *list);//初始化循环单链表
 void push_back(List *list, ElemType x);//在循环单链表的末尾插入元素
 void push_front(List *list, ElemType x);//在循环单链表的头部插入元素
 void show_list(List *list);//打印循环单链表
 void pop_back(List *list);//删除循环单链表的最后一个元素
 void pop_front(List *list);//删除循环单链表的第一个元素
 void insert_val(List *list, ElemType val);//将数据元素插入到循环单链表中（要求此时循环单链表中的数据元素顺序排列）
 Node* find(List *list, ElemType x);//查找循环单链表中数据值为x的结点
 int length(List *list);//求循环单链表的长度
 void delete_val(List *list, ElemType x);//按值删除循环单链表中的某个数据元素
 void sort(List *list);//对循环单链表进行排序
 void reverse(List *list);//逆置循环单链表
 void clear(List *list);//清除循环单链表
 void destroy(List *list);//摧毁循环单链表

 //优化
 Node* _buynode(ElemType x);//创建结点

 #endif

SClist.cpp

 #include"SClist.h"

 Node* _buynode(ElemType x) {
     Node *s = (Node*)malloc(sizeof(Node));
     assert(s != NULL);
     s->data = x;
     s->next = NULL;
     return s;
 }

 void InitSClist(List *list) {
     Node *s = (Node*)malloc(sizeof(Node));
     assert(s != NULL);
     list->first = list->last = s;
     list->last->next = list->first;//让链表最后一个结点的指针域指向头结点，从而时链表循环
     list->size = ;
 }

 void push_back(List *list, ElemType x) {
     Node *s = _buynode(x);
     list->last->next = s;
     list->last = s;
 23     list->last->next = list->first;
     list->size++;
 }

 void push_front(List *list, ElemType x) {
     Node *s = _buynode(x);
     s->next = list->first->next;
     list->first->next = s;
 31     if (list->last == list->first)
 32         list->last = s;
     list->size++;
 }

 void show_list(List *list) {
     Node *p = list->first->next;
     while (p != list->first) {
         printf("%d->", p->data);
         p = p->next;
     }
     printf("Nul.\n");
 }

 void pop_back(List *list) {
     if (list->size == ) return;
     Node *p = list->first;
     while (p->next != list->last)
         p = p->next;
     free(list->last);
     list->last = p;
 52     list->last->next = list->first;
     list->size--;
 }

 void pop_front(List *list) {
     if (list->size == ) return;
     Node *p = list->first->next;
     list->first->next = p->next;
 60     if (list->size == 1)
 61         list->last = list->first;
     free(p);
     list->size--;
 }

 void insert_val(List *list, ElemType x) {
     Node *p = list->first;
     while (p->next != list->last && p->next->data < x)
         p = p->next;
     if (p->next == list->last && p->next->data < x)
         push_back(list, x);
     else {
         Node *s = _buynode(x);
         s->next = p->next;
         p->next = s;
         list->size++;
     }
 }

 Node* find(List *list, ElemType key) {
     if (list->size == ) return NULL;
     Node *p = list->first->next;
     while(p != list->first && p->data != key)
         p = p->next;
 85     if (p == list->first)
 86         return NULL;
     return p;
 }

 int length(List *list) {
     return list->size;
 }

 void delete_val(List *list, ElemType x) {
     if (list->size == ) return;
     Node *p = find(list, x);
     if (p == NULL) {
         printf("没有要删除的数据!\n");
         return;
     }
     if (p == list->last)
         pop_back(list);
     else {
         Node *q = p->next;
         p->data = q->data;
         p->next = q->next;
         free(q);
         list->size--;
     }
 }

 void sort(List *list) {
     if (list->size ==  || list->size == ) return;
     Node *s = list->first->next;
     Node *q = s->next;
     list->last->next = NULL;
     list->last = s;
     list->last->next = list->first;
     while (q != NULL) {
         s = q;
         q = q->next;
         Node *p = list->first;
         while (p->next != list->last && p->next->data < s->data)
             p = p->next;
         if (p->next == list->last &&p->next->data < s->data) {
             list->last->next = s;
             list->last = s;
             list->last->next = list->first;
         }
         else {
             s->next = p->next;
             p->next = s;
         }
     }
 }

 void reverse(List *list) {
     if (list->size ==  || list->size == ) return;
     Node *p = list->first->next;
     Node *q = p->next;
     list->last->next = NULL;
     list->last = p;
     list->last->next = list->first;
     while (q != NULL) {
         p = q;
         q = q->next;
         p->next = list->first->next;
         list->first->next = p;
     }
 }

 void clear(List *list) {
     Node *p = list->first->next;
     while (p != list->first) {
         list->first->next = p->next;
         free(p);
         p = list->first->next;
     }
     list->last = list->first;
     list->last->next = list->first;
     list->size = ;
 }

 void destroy(List *list) {
     clear(list);
     free(list->first);
     list->first = list->last = NULL;
 }

main.cpp

 #include"SClist.h"

 void main() {
     List mylist;
     InitSClist(&mylist);

     ElemType item;
     Node *p = NULL;
     int select = ;
     while (select) {
         printf("*******************************************\n");
         printf("*[1]  push_back        [2]  push_front    *\n");
         printf("*[3]  show_list        [4]  pop_back      *\n");
         printf("*[5]  pop_front        [6]  insert_val    *\n");
         printf("*[7]  find             [8]  length        *\n");
         printf("*[9]  delete_val       [10] sort          *\n");
         printf("*[11] reverse          [12] clear         *\n");
         printf("*[13*] destroy         [0]  quit_system   *\n");
         printf("*******************************************\n");
         printf("请选择：>>");
         scanf("%d", &select);
         if (select == ) break;
         switch (select) {
         case :
             printf("请输入要插入的数据（-1结束）:>");
             while (scanf("%d", &item), item != -) {
                 push_back(&mylist, item);
             }
             break;
         case :
             printf("请输入要插入的数据（-1结束）:>");
             while (scanf("%d", &item), item != -) {
                 push_front(&mylist, item);
             }
             break;
         case :
             show_list(&mylist);
             break;
         case :
             pop_back(&mylist);
             break;
         case :
             pop_front(&mylist);
             break;
         case :
             printf("请输入要插入的数据:>");
             scanf("%d", &item);
             insert_val(&mylist, item);
             break;
         case :
             printf("请输入要查找的数据:>");
             scanf("%d", &item);
             p = find(&mylist, item);
             if (p == NULL)
                 printf("要查找的数据在单链表中不存在！\n");
             break;
         case :
             printf("单链表的长度为%d\n", length(&mylist));
             break;
         case :
             printf("请输入要删除的值:>");
             scanf("%d", &item);
             delete_val(&mylist, item);
             break;
         case :
             sort(&mylist);
             break;
         case :
             reverse(&mylist);
             break;
         case :
             clear(&mylist);
             break;
             //case 13:
             //destroy(&mylist);
             //break;
         default:
             printf("选择错误,请重新选择！\n");
             break;
         }
     }
     destroy(&mylist);
 }