1.#include <stdio.h>
#include <malloc.h>
#include "CircleList.h"

typedef struct _tag_CircleList
{
    CircleListNode header;
    CircleListNode* slider;
    int length;
} TCircleList;

CircleList* CircleList_Create() // O(1)
{
    TCircleList* ret = (TCircleList*)malloc(sizeof(TCircleList));
    
    if( ret != NULL )
    {
        ret->length = 0;
        ret->header.next = NULL;
        ret->slider = NULL;
    }
    
    return ret;
}

void CircleList_Destroy(CircleList* list) // O(1)
{
    free(list);
}

void CircleList_Clear(CircleList* list) // O(1)
{
    TCircleList* sList = (TCircleList*)list;
    
    if( sList != NULL )
    {
        sList->length = 0;
        sList->header.next = NULL;
        sList->slider = NULL;
    }
}

int CircleList_Length(CircleList* list) // O(1)
{
    TCircleList* sList = (TCircleList*)list;
    int ret = -1;
    
    if( sList != NULL )
    {
        ret = sList->length;
    }
    
    return ret;
}

int CircleList_Insert(CircleList* list, CircleListNode* node, int pos) // O(n)
{
    TCircleList* sList = (TCircleList*)list;
    int ret = (sList != NULL) && (pos >= 0) && (node != NULL);
    int i = 0;
    
    if( ret )
    {
        CircleListNode* current = (CircleListNode*)sList;
        
        for(i=0; (i<pos) && (current->next != NULL); i++)
        {
            current = current->next;
        }
        
        node->next = current->next;
        current->next = node;
        
        if( sList->length == 0 )
        {
            sList->slider = node;
            node->next = node;
        }
        
        sList->length++;
    }
    
    return ret;
}

CircleListNode* CircleList_Get(CircleList* list, int pos) // O(n)
{
    TCircleList* sList = (TCircleList*)list;
    CircleListNode* ret = NULL;
    int i = 0;
    
    if( (sList != NULL) && (pos >= 0) )
    {
        CircleListNode* current = (CircleListNode*)sList;
        
        for(i=0; i<pos; i++)
        {
            current = current->next;
        }
        
        ret = current->next;
    }
    
    return ret;
}

CircleListNode* CircleList_Delete(CircleList* list, int pos) // O(n)
{
    TCircleList* sList = (TCircleList*)list;
    CircleListNode* ret = NULL;
    int i = 0;
    
    if( (sList != NULL) && (pos >= 0) )
    {
        CircleListNode* current = (CircleListNode*)sList;
        CircleListNode* first = sList->header.next;//获取第一个元素
        //获取最后一个元素
        CircleListNode* last = (CircleListNode*)CircleList_Get(sList, sList->length - 1);
        
        for(i=0; i<pos; i++)
        {
            current = current->next;
        }
        //删除code
        ret = current->next;
        current->next = ret->next;
        
        sList->length--;
        
        if( first == ret )
        {
            sList->header.next = ret->next;
            last->next = ret->next;
        }
        
        if( sList->slider == ret )
        {
            sList->slider = ret->next;
        }
        
        if( sList->length == 0 )
        {
            sList->header.next = NULL;
            sList->slider = NULL;
        }
    }
    
    return ret;
}
//以下是游标的操作
CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node) // O(n)
{
    TCircleList* sList = (TCircleList*)list;
    CircleListNode* ret = NULL;
    int i = 0;
    
    if( sList != NULL )
    {
        CircleListNode* current = (CircleListNode*)sList;
        
        for(i=0; i<sList->length; i++)
        {
        //查找游标的逻辑位置
            if( current->next == node )
            {
                ret = current->next;
                break;
            }
            
            current = current->next;
        }
        
        if( ret != NULL )
        {
            CircleList_Delete(sList, i);
        }
    }
    
    return ret;
}
//重新设置---将游标重新置位
CircleListNode* CircleList_Reset(CircleList* list) // O(1)
{
    TCircleList* sList = (TCircleList*)list;
    CircleListNode* ret = NULL;
    
    if( sList != NULL )
    {
        sList->slider = sList->header.next;
        ret = sList->slider;
    }
    
    return ret;
}

CircleListNode* CircleList_Current(CircleList* list) // O(1)
{
    TCircleList* sList = (TCircleList*)list;
    CircleListNode* ret = NULL;
    
    if( sList != NULL )
    {
        ret = sList->slider;
    }
    
    return ret;
}
//当前的游标指向下一个
CircleListNode* CircleList_Next(CircleList* list) // O(1)
{
    TCircleList* sList = (TCircleList*)list;
    CircleListNode* ret = NULL;
    
    if( (sList != NULL) && (sList->slider != NULL) )
    {
        ret = sList->slider;
        sList->slider = ret->next;
    }
    
    return ret;
}

2.#ifndef _CIRCLELIST_H_
#define _CIRCLELIST_H_

typedef void CircleList;
typedef struct _tag_CircleListNode CircleListNode;
struct _tag_CircleListNode
{
    CircleListNode* next;
};

CircleList* CircleList_Create();

void CircleList_Destroy(CircleList* list);

void CircleList_Clear(CircleList* list);

int CircleList_Length(CircleList* list);

int CircleList_Insert(CircleList* list, CircleListNode* node, int pos);

CircleListNode* CircleList_Get(CircleList* list, int pos);

CircleListNode* CircleList_Delete(CircleList* list, int pos);

CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node);

CircleListNode* CircleList_Reset(CircleList* list);

CircleListNode* CircleList_Current(CircleList* list);

CircleListNode* CircleList_Next(CircleList* list);

#endif

3.#include <stdio.h>
#include <stdlib.h>
#include "CircleList.h"

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

struct Value
{
    CircleListNode header;
    int v;
};

int main(int argc, char *argv[])
{
    int i = 0;
    //create circular list
    CircleList* list = CircleList_Create();
    
    struct Value v1;
    struct Value v2;
    struct Value v3;
    struct Value v4;
    struct Value v5;
    struct Value v6;
    struct Value v7;
    struct Value v8;
    
    v1.v = 1;
    v2.v = 2;
    v3.v = 3;
    v4.v = 4;
    v5.v = 5;
    v6.v = 6;
    v7.v = 7;
    v8.v = 8;
    //测试数据
    CircleList_Insert(list, (CircleListNode*)&v1, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v2, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v3, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v4, CircleList_Length(list));
    
    CircleList_Insert(list, (CircleListNode*)&v5, 5);
    CircleList_Delete(list, 0);
    
    for(i=0; i<2*CircleList_Length(list); i++)
    {
        struct Value* pv = (struct Value*)CircleList_Get(list, i);
        
        printf("%d\n", pv->v);
    }
    
    printf("\n");
    
    while( CircleList_Length(list) > 0 )
    {
        struct Value* pv = (struct Value*)CircleList_Delete(list, 0);
        
        printf("%d\n", pv->v);
    }
    
    printf("\n");
    //实现循环问题--读数
    CircleList_Insert(list, (CircleListNode*)&v1, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v2, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v3, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v4, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v5, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v6, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v7, CircleList_Length(list));
    CircleList_Insert(list, (CircleListNode*)&v8, CircleList_Length(list));
    //直接移动--游标
    for(i=0; i<CircleList_Length(list); i++)
    {
        struct Value* pv = (struct Value*)CircleList_Next(list);
        
        printf("%d\n", pv->v);
    }
    
    printf("\n");
    
    CircleList_Reset(list);
    
    while( CircleList_Length(list) > 0 )
    {
        struct Value* pv = NULL;
        
        for(i=1; i<3; i++)
        {
            CircleList_Next(list);
        }
        
        pv = (struct Value*)CircleList_Current(list);
        
        printf("%d\n", pv->v);
        
        CircleList_DeleteNode(list, (CircleListNode*)pv);
    }
    
    CircleList_Destroy(list);
    
    return 0;
}

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