数据结构-循环链表（学习笔记）

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

游标：

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。

一些新的操作：

1.获取当前游标指向的数据元素

2.将游标重置指向链表中的第一个数据元素

3.将游标移动指向到链表中的下一个数据元素

4.直接指定删除链表中的某个数据元素

头文件:

#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

c文件

#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;        //查找pos的元素         for(i=0; (i<pos) && (current->next != NULL); i++)        {            current = current->next;        }        //插入元素         node->next = current->next;        current->next = node;        //如果只有一个元素则自己指向自己         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;        CircleListNode* last = (CircleListNode*)CircleList_Get(sList, sList->length - 1);                for(i=0; i<pos; i++)        {            current = current->next;        }                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;}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++)        {            if( current->next == node )            {                ret = current->next;                break;            }                        current = current->next;        }                if( ret != NULL )        {            CircleList_Delete(sList, i);        }    }        return ret;}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;}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;}

main文件：

#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;};/* run this program using the console pauser or add your own getch, system("pause") or input loop */int main(int argc, char *argv[]) {int i = 0;    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;        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");        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));        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;}

运行结果：

总结：

1.循环链表只是在单链表的基础上做了一个加强

2. 循环链表可以完全取代单链表的使用

3.循环链表的Next和Current操作可以高效的遍历链表中的所有元素