循环链表设计与API实现

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所有操作

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

在循环链表中可以定义一个“当前”指针，这个指针通常称为游标，可以通过这个游标来遍历链表中的所有元素。

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);

// 根据元素的值 删除 元素 pk根据元素的位置 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 开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 个人开始从 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);

// 根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;

	// 如果是第一次插入
	if (tList->length == 0) {
		tList->silder = node;
	}

	++tList->length; // 记得长度加1

	// 如果是头插法
	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)
{
	// 因为是循环链表，所以这里不需要排除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，需要求出尾结点
		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0
		if (tList->length == 0) {
			tList->header.next = NULL;
			tList->silder = NULL;
		}
	}

	return ret;
}

// 根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;
		}

		// 如果找到
		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); //根据结点的值,进行结点元素的删除
	}
	printf("\n");

	CircleList_Destroy(list);

}

// main.cpp
// 循环链表测试程序

#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，可以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(); // 为了测试数据的生命周期，所以另写一个函数调用运行
	joseph();

	return 0;
}

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