數據結構：循環鏈表的c語言實現

circlelist .h

#ifndef _MYCIRCLELIST_H_
#define _MYCIRCLELIST_H_


#include<stdio.h>
#include<stdlib.h>
#include<string.h>

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


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);
//直接指定刪除鏈表中的某個數據元素
CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node);
//將遊標重置指向鏈表中的第一個元素
CircleListNode* CircleList_Reset(CircleList* list);
//獲取當前遊標指向的數據元素
CircleListNode* CircleList_Current(CircleList* list);
CircleListNode* CircleList_Next(CircleList* list);
#endif // !_MYCIRCLELIST_H_

頭文件中定義鏈表結點

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

circlelist.c

#include"circlelist.h"
typedef struct _tag_CircleList
{
	CircleListNode header;
	CircleListNode* slider;    //遊標是比鏈表新增的
	int length;
}TCircleList;

CircleList* CircleList_Create() 
{
	TCircleList * ret = (TCircleList*)malloc(sizeof(TCircleList));
	if (ret == NULL)
	{
		return NULL;
	}
	ret->length = 0;
	ret->header.next = NULL;
	ret->slider = NULL;
	return ret;
}
void CircleList_Destroy(CircleList* list)
{
	if (list != NULL)
	{
		free(list);
		return;
	}
	return;
}
void CircleList_Clear(CircleList* list)
{
	TCircleList* sList = (TCircleList*)list;
	if (sList == NULL)
	{
		return; 
	}
	sList->length = 0;
	sList->header.next = NULL;
	sList->slider = NULL;
	return;
}

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

}

int CircleList_Insert(CircleList* list, CircleListNode* node, int pos)
{
	int ret = 0, i = 0;
	TCircleList* sList = (TCircleList*)list;

	if (list == NULL || node == NULL || pos < 0)
	{
		return -1;
	}
	CircleListNode* current = (CircleListNode*)sList;
	for (i = 0; (i < pos) && (current->next != NULL); i++)
	{
		current = current->next;
	}
	node->next = current->next;  //1
	current->next = node;   //2

	//若第一次插入節點

	if (sList->length == 0)
	{
		sList->slider = node;
	}

	sList->length++;

	//如果是頭插法
	if (current == (CircleListNode*)sList)
	{
		//獲取最後一個元素
		CircleListNode* last = CircleList_Get(sList, sList->length - 1);
		last->next = current->next;  //3

	}

	return 0;
}

CircleListNode* CircleList_Get(CircleList* list, int pos)
{
	TCircleList* sList = (TCircleList*)list;
	CircleListNode* ret = NULL;
	int i = 0;

	if (list == NULL || pos < 0)
	{
		return NULL;
	}

	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)
{

	TCircleList *sList = (TCircleList*)list;
	CircleListNode* ret = NULL;
	int i = 0;

	if ((sList != NULL) && (pos >= 0) && (sList->length > 0))
	{
		CircleListNode* current = (CircleListNode*)sList;
		//CircleListNode* current = (CircleListNode*)(&(sList->header));
		CircleListNode* last = NULL;

		for (i = 0; i < pos; i++)
		{
			current = current->next;
		}
		//若刪除第一個元素
		if (current == (CircleListNode*)sList)
		{
			last = (CircleListNode*)CircleList_Get(sList, sList->length - 1);
		}
		ret = current->next;
		current->next = ret->next;

		sList->length--;

		if (last != NULL)  
		{
			sList->header.next = ret->next;
			last->next = ret->next;
		}
		//若刪除元素爲遊標所指元素
		if (sList->slider == ret)
		{
			sList->slider = ret->next;
		}
		//若刪除元素後鏈表長度爲0
		if (sList->length == 0)
		{
			sList->header.next = NULL;
			sList->slider = NULL;
		}

	}
		return ret;
}

//直接指定刪除鏈表中的某個數據元素
CircleListNode* CircleList_DeleteNode(CircleList* list, CircleListNode* node)
{
	TCircleList* sList = (TCircleList*)list;
	CircleListNode* ret = NULL;
	int i = 0;

	if (sList != NULL)
	{
		CircleListNode* current = (CircleListNode*)sList;
		//查找node在循環鏈表中的位置i
		for (i = 0; i < sList->length; i++)
		{
			if (current->next == node)    //是結點的位置，也是業務結點的存儲位置
			{
				ret = current->next;
				break;
			}
			current = current->next;
		}
		if(ret!=NULL)
		{
			CircleList_Delete(sList, i);

		 }
	}
	return ret;
}
//將遊標重置指向鏈表中的第一個元素,並返回
CircleListNode* CircleList_Reset(CircleList* list)
{
	TCircleList* sList = (TCircleList*)list;
	CircleListNode* ret = NULL;
	if (sList != NULL)
	{
		sList->slider = sList->header.next;
		ret = sList->slider;
	}
	return ret;
}
//獲取當前遊標指向的數據元素
CircleListNode* CircleList_Current(CircleList* list)
{
	TCircleList* sList = (TCircleList*)list;
	CircleListNode* ret = NULL;
	if (sList != NULL)
	{
		ret = sList->slider;
	}
	return ret;
}

CircleListNode* CircleList_Next(CircleList* list)
{
	TCircleList* sList = (TCircleList*)list;
	CircleListNode * ret = NULL;
	if ((sList != NULL) && (sList->slider != NULL))
	{
		ret = sList->slider;
		sList->slider = ret->next;
	}
	return ret;
}

循環鏈表一是要把尾部結點的next指向頭結點
二是多了一個遊標來尋找當前結點。