双循环链表的基本操作（不带头结点）

1. Node.h

#ifndef NODE_H
#define NODE_H

#include 
#include 

typedef struct NODE
{
    int value;
    struct NODE *prior, *next;

}Node, *DNode;

#endif

1. List.h

#ifndef LIST_H
#define LIST_H

#include "Node.h"

//初始化链表
void InitDouLinkList(DNode *pHead);
//头插建表
void InsertByHead(DNode *pHead, int value);
//尾插建表
void InsertByTail(DNode *pHead, int value);
//获取链表长度
int  GetLength(DNode pHead);
//正向显示链表
void ShowDouLinkList(DNode pHead);
//反向显示链表
void ReverseShowLinkList(DNode pHead);
//头删
void DeleteByHead(DNode *pHead);
//尾删
void DeleteByTail(DNode *pHead);
//按值查找
DNode FindByValue(DNode pHead, int value);
//按索引查找
DNode FindByIndex(DNode pHead, int index);
void InsertByIndex(DNode *pHead, int index, int value);
//按索引删除
void DeleteByIndex(DNode* pHead, int index);
// 按索引修改
void UpdateByIndex(DNode pHead, int index, int value);
//按值修改
void UpdateByValue(DNode pHead, int oldval, int newval);
//按值删除
void DeleteByValue(DNode *pHead, int value);
//清空双链表(保留头结点）
void Clear(DNode* pHead);

#endif

1. List.c

#include "Node.h"

void InitDouLinkList(DNode *pHead)
{
    *pHead = (DNode)malloc(sizeof(Node));
    (*pHead)->prior = *pHead;
    (*pHead)->next = *pHead;
}


void InsertByHead(DNode *pHead, int value)
{
    DNode pNew = (DNode)malloc(sizeof(Node));
    pNew->value = value;
    if ((*pHead)->next == *pHead || (*pHead)->prior == *pHead)
    {
        (*pHead)->next = pNew;
        (*pHead)->prior = pNew;
        pNew->next = *pHead;
        pNew->prior = *pHead;

    }
    else
    {


        (*pHead)->next->prior = pNew;
        pNew->next = (*pHead)->next;
        pNew->prior = (*pHead);
        (*pHead)->next = pNew;



    }


}


void InsertByTail(DNode *pHead, int value)
{

    if ((*pHead)->next == *pHead || (*pHead)->prior == *pHead)
    {
        InsertByHead(pHead, value);

    }
    else
    {
        DNode pNew = (DNode)malloc(sizeof(Node));
        pNew->value = value;
        (*pHead)->prior->next = pNew;
        pNew->prior = (*pHead)->prior;
        pNew->next = *pHead;
        (*pHead)->prior = pNew;



    }


}


int  GetLength(DNode pHead)
{
    int count = 0;
    DNode pos = pHead;
    while (pos->next != pHead)
    {
        pos = pos->next;
        count++;
    }
    return count;

}


void ShowDouLinkList(DNode pHead)
{
    DNode pos = pHead;
    while (pos->next != pHead)
    {
        pos = pos->next;
        //pHead里面存的是第一个结点的地址,pHead->next->value是第一个数
        printf("%d\t", pos->value);
    }


}


void ReverseShowLinkList(DNode pHead)
{
    DNode pos = pHead;
    while (pos->prior != pHead)
    {

        pos = pos->prior;
        printf("%d\t", pos->value);
    }

}


void DeleteByHead(DNode *pHead)
{
    if ((*pHead)->next != *pHead || (*pHead)->prior != *pHead)
    {
        DNode temp = (*pHead)->next;
        (*pHead)->next = temp->next;
        temp->next->prior = (*pHead);
        free(temp);
        temp = NULL;

    }


}


void DeleteByTail(DNode *pHead)
{
    if ((*pHead)->next != *pHead || (*pHead)->prior != *pHead)
    {
        DNode temp = (*pHead)->prior;
        temp->prior->next = *pHead;
        *pHead = temp->next;
        free(temp);
        temp = NULL;
    }


}


DNode FindByValue(DNode pHead, int value)
{
    DNode pos = pHead;
    while (pos->value != value&&pos->next != pHead)
    {
        pos = pos->next;
    }
    return pos;
}


DNode FindByIndex(DNode pHead, int index)
{
    DNode pos = pHead;
    if (index >0 && indexfor (int i = 0; i <= index; i++)
        {
            pos = pos->next;
        }

    }
    return pos;


}


void InsertByIndex(DNode *pHead, int index, int value)
{
    if (0 == index)
    {
        InsertByHead(pHead, value);
    }
    else if (index > 0 && index <= GetLength(*pHead))
    {
        DNode pos = *pHead;
        for (int i = 0; i < index && pos->next != *pHead; i++)
        {
            pos = pos->next;
        }
        DNode pNew = (DNode)malloc(sizeof(Node));
        pNew->value = value;
        pNew->next = pos->next;
        pos->prior = pNew;
        pNew->prior = pos;
        pos->next = pNew;
    }

}


void DeleteByIndex(DNode* pHead, int index)
{
    DNode pos = FindByIndex(*pHead, index);
    if (pos != NULL)
    {
        if (pos->next != *pHead)
        {
            pos->prior->next = pos->next;
            pos->next->prior = pos->prior;
            free(pos);
            pos = NULL;
        }
        else
        {
            pos->prior->next = pos->next;
            pos->next->prior = pos->prior;
            free(pos);
            pos = NULL;

        }
    }


}

void UpdateByIndex(DNode pHead, int index, int value)
{
    DNode pos = FindByIndex(pHead, index);
    if (pos != NULL)
    {
        pos->value = value;

    }
}


void UpdateByValue(DNode pHead, int oldval, int newval)
{
    DNode pos = FindByValue(pHead, oldval);
    while (pos != NULL&&pos->value == oldval)
    {
        pos->value = newval;
        pos = FindByValue(pHead, oldval);
    }

}


void DeleteByValue(DNode *pHead, int value)
{
    DNode pos = FindByValue(*pHead, value);
    while (pos != NULL&&pos->next != *pHead)
    {
        pos->prior->next = pos->next;
        pos->next->prior = pos->prior;
        free(pos);
        pos = NULL;
        pos = FindByValue(*pHead, value);
    }
    if (pos->next == *pHead && pos != NULL)
    {
        DeleteByTail(pHead);
    }
}


void Clear(DNode* pHead)
{

    while ((*pHead)->next != *pHead || (*pHead)->prior != *pHead)
    {

        DeleteByTail(pHead);
    }

}

1. main.c

#include "Node.h"
#include "List.h"

int main(void)
{
    DNode pHead = NULL;
    InitDouLinkList(&pHead);
    //InsertByHead(&pHead, 1);
    //InsertByHead(&pHead, 2);
   // InsertByHead(&pHead, 3);
    //InsertByHead(&pHead, 4);
    InsertByTail(&pHead, 5);
    InsertByTail(&pHead, 7);
    InsertByTail(&pHead, 8);
    InsertByTail(&pHead, 7);
    InsertByTail(&pHead, 8);
    //InsertByIndex(&pHead, 4, 55);
 //UpdateByValue(pHead, 8, 88);


    //DeleteByHead(&pHead);
    //DeleteByTail(&pHead);
    //UpdateByIndex(pHead, 4, 88);
    //DeleteByIndex(&pHead, 4);


    Clear(&pHead);
    ShowDouLinkList(pHead);
    //ReverseShowLinkList(pHead);

    return 0;
}