基本概念
循环链表的定义：将单链表中最后一个数据元素的next指针指向第一个元素

循环链表拥有单链表的全部操作

创建链表
销毁链表
获取链表长度
清空链表
获取第pos个元素操作
插入元素到位置pos
删除位置pos处的元素

新增功能：游标的定义

在循环链表中能够定义一个“当前”指针，这个指针通常称为游标，能够通过这个游标来遍历链表中的全部元素。

循环链表新操作

将游标重置指向链表中的第一个数据元素
CircleListNode* CircleList_Reset(CircleList* list);

获取当前游标指向的数据元素
CircleListNode* CircleList_Current(CircleList* list);

将游标移动指向到链表中的下一个数据元素
CircleListNode* CircleList_Next(CircleList* list);

直接指定删除链表中的某个数据元素
CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node);
// 依据元素的值 删除 元素 pk依据元素的位置 删除 元素

最后加了一个循环链表的应用：求解约瑟夫问题

约瑟夫问题-循环链表典型应用
n 个人围成一个圆圈，首先第 1 个人从 1 開始一个人一个人顺时针报数，报到第 m 个人，令其出列。

然后再从下一 个人開始从 1 顺时针报数，报到第 m 个人。再令其出列，…。如此下去，求出列顺序。

代码：

// circlelist.h
// 循环链表API声明#ifndef _CIRCLELIST_H_
#define _CIRCLELIST_H_typedef void CircleList;typedef struct _tag_CircleListNode
{struct _tag_CircleListNode *next;
}CircleListNode;// 创建链表
CircleList* CircleList_Create();// 销毁链表
void CircleList_Destroy(CircleList* list);// 清空链表
void CircleList_Clear(CircleList* list);// 获取链表的长度
int CircleList_Length(CircleList* list);// 在pos位置插入结点node
int CircleList_Insert(CircleList* list,CircleListNode* node, int pos);// 获取pos位置的结点
CircleListNode* CircleList_Get(CircleList* list, int pos);// 删除pos位置的结点
CircleListNode* CircleList_Delete(CircleList* list, int pos);// 依据结点的值进行数据删除
CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node);// 重置游标
CircleListNode* CircleList_Reset(CircleList* list);// 获取当前游标所指结点
CircleListNode* CircleList_Current(CircleList* list);// 将原始游标所指结点返回给上层，然后让游标移到下一个结点
CircleListNode* CircleList_Next(CircleList* list);#endif

// circlelist.cpp
// 循环链表API实现#include <iostream>
#include <cstdio>
#include "circlelist.h"typedef struct _tag_CircleList
{CircleListNode header;CircleListNode *silder;int length;
}TCircleList;// 创建链表
CircleList* CircleList_Create()
{TCircleList *ret = (TCircleList *)malloc(sizeof(TCircleList));if (ret == NULL) {return NULL;}// 初始化ret->header.next = NULL;ret->silder = NULL;ret->length = 0;return ret;
}// 销毁链表
void CircleList_Destroy(CircleList* list)
{if (list == NULL) {return;}free(list);return;
}// 清空链表
void CircleList_Clear(CircleList* list)
{if (list == NULL) {return;}TCircleList *tList = (TCircleList *)list;tList->header.next = NULL;tList->silder = NULL;tList->length = 0;return;
}// 获取链表的长度
int CircleList_Length(CircleList* list)
{if (list == NULL) {return -1;}TCircleList *tList = (TCircleList *)list;return tList->length;
}// 在pos位置插入结点node
int CircleList_Insert(CircleList* list, CircleListNode* node, int pos)
{if (list == NULL || node == NULL || pos < 0) {return -1;}TCircleList *tList = (TCircleList *)list;CircleListNode *cur = (CircleListNode *)tList;for (int i = 0; i < pos; ++i) {cur = cur->next;}node->next = cur->next;cur->next = node;// 假设是第一次插入if (tList->length == 0) {tList->silder = node;}++tList->length; // 记得长度加1// 假设是头插法if (cur == (CircleListNode *)tList) {// 获取最后一个元素CircleListNode *last = CircleList_Get(tList, tList->length - 1);last->next = cur->next;}return 0;
}// 获取pos位置的结点
CircleListNode* CircleList_Get(CircleList* list, int pos)
{// 由于是循环链表，所以这里不须要排除pos>length的情况if (list == NULL || pos < 0) {return NULL;}TCircleList *tList = (TCircleList *)list;CircleListNode *cur = (CircleListNode *)tList;for (int i = 0; i < pos; ++i) {cur = cur->next;}return cur->next;
}// 删除pos位置的结点
CircleListNode* CircleList_Delete(CircleList* list, int pos)
{TCircleList *tList = (TCircleList *)list;CircleListNode *ret = NULL;if (tList != NULL && pos >= 0 && tList->length > 0) {CircleListNode *cur = (CircleListNode *)tList;for (int i = 0; i < pos; ++i) {cur = cur->next;}// 若删除头结点，须要求出尾结点CircleListNode *last = NULL;if (cur == (CircleListNode *)tList)  {last = CircleList_Get(tList, tList->length - 1);}ret = cur->next;cur->next = ret->next;--tList->length;// 若删除头结点if (last != NULL) {tList->header.next = ret->next;last->next = ret->next;}// 若删除的元素为游标所指的元素if (tList->silder == ret) {tList->silder = ret->next;}// 若删除元素后链表长度为0if (tList->length == 0) {tList->header.next = NULL;tList->silder = NULL;}}return ret;
}// 依据结点的值进行数据删除
CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node)
{TCircleList *tList = (TCircleList *)list;CircleListNode *ret = NULL;if (list != NULL && node != NULL) {CircleListNode *cur = (CircleListNode *)tList;int i = 0;for (i = 0; i < tList->length; ++i) {if (cur->next == node) {ret = cur->next;break;}cur = cur->next;}// 假设找到if (ret != NULL) {CircleList_Delete(tList, i);}}return ret;
}// 重置游标
CircleListNode* CircleList_Reset(CircleList* list)
{TCircleList *tList = (TCircleList *)list;CircleListNode* ret = NULL;if (list != NULL) {tList->silder = tList->header.next;ret = tList->silder;}return NULL;
}// 获取当前游标所指结点
CircleListNode* CircleList_Current(CircleList* list)
{TCircleList *tList = (TCircleList *)list;CircleListNode* ret = NULL;if (list != NULL) {ret = tList->silder;}return ret;
}// 将原始游标所指结点返回给上层，然后让游标移到下一个结点
CircleListNode* CircleList_Next(CircleList* list)
{TCircleList *tList = (TCircleList *)list;CircleListNode* ret = NULL;if (list != NULL && tList->silder != NULL) {ret = tList->silder;tList->silder = ret->next;}return ret;
}

// joseph.h
// 用循环链表API求解约瑟夫问题#include <cstdio>
#include "circlelist.h"const int maxp = 8;struct Person
{CircleListNode circlenode;int id;
};void joseph()
{Person s[maxp];for (int i = 0; i < maxp; ++i) {s[i].id = i + 1;}CircleList *list = NULL;list = CircleList_Create();// 插入元素for (int i = 0; i < maxp; ++i) {// 尾插法int ret = CircleList_Insert(list, (CircleListNode *)&s[i], CircleList_Length(list));if (ret < 0) {printf("function CircleList_Insert err: %d\n", ret);}}// 遍历链表for (int i = 0; i < CircleList_Length(list); ++i) {Person *tmp = (Person *)CircleList_Get(list, i);if (tmp == NULL) {printf("function CircleList_Get err.\n");}printf("age: %d\n", tmp->id);}// 求解约瑟夫问题while (CircleList_Length(list) > 0){Person* pv = NULL;for (int i = 1; i < 3; i++){CircleList_Next(list);}pv = (Person*)CircleList_Current(list);printf("%d ", pv->id);CircleList_DeleteNode(list, (CircleListNode *)pv); //依据结点的值,进行结点元素的删除}printf("\n");CircleList_Destroy(list);}

// main.cpp
// 循环链表測试程序#include <iostream>
#include <cstdio>
#include "circlelist.h"
#include "joseph.h"const int maxn = 5;struct Student
{CircleListNode circlenode;char name[32];int age;
};void play01()
{Student s[maxn];for (int i = 0; i < maxn; ++i) {s[i].age = i + 1;}CircleList *list = NULL;list = CircleList_Create(); // 创建链表// 插入元素for (int i = 0; i < maxn; ++i) {// 尾插法int ret = CircleList_Insert(list, (CircleListNode *)&s[i], CircleList_Length(list));if (ret < 0) {printf("function CircleList_Insert err: %d\n", ret);}}// 遍历链表// 这里遍历打印两边，能够证明这是一个循环链表for (int i = 0; i < 2 * CircleList_Length(list); ++i) {Student *tmp = (Student *)CircleList_Get(list, i);if (tmp == NULL) {printf("function CircleList_Get err.\n");}printf("age: %d\n", tmp->age);}// 删除结点，通过结点位置while (CircleList_Length(list)) {Student *tmp = (Student *)CircleList_Delete(list, CircleList_Length(list) - 1);if (tmp == NULL) {printf("function CircleList_Delete err.\n");}printf("age: %d\n", tmp->age);}// 销毁链表CircleList_Destroy(list);}int main()
{play01(); // 为了測试数据的生命周期，所以另写一个函数调用执行joseph();return 0;
}