双向循环链表

双向循环链表:
1.首先,双向链表通常采用带表头结点的循环链表形式,即双向循环链表。双向循环链表在双向链表的基础上,将表头结点的前驱指针指向尾结点,尾结点的后驱指针指向头结点,首尾相连形成一个双向环。双向循环链表可方便地获取当前结点的前驱结点,不必像单向循环链表那样从头开始遍历;而其循环的特性又可方便地从任一结点出发单向遍历整个链表,不必像双向链表那样根据方向而使用不同的指针域。

2.如图所示:
双向循环链表_第1张图片

3.代码如下:

#include"stdio.h"
#include"stdlib.h"
#include"assert.h"
#pragma warning (disable:4996)

typedef int DataType;
typedef struct DCLNode
{
    struct DCLNode* _pNext;
    struct DCLNode* _pPre;
    DataType _data;
}Node, *PNode;

//初始化双向循环列表
void DCLInit(PNode* ppHead)
{
    assert(ppHead);
    *ppHead = (PNode)malloc(sizeof(Node));
    if (NULL == *ppHead)
        assert(0);
    (*ppHead)->_pNext = *ppHead;
    (*ppHead)->_pPre = *ppHead;
}

//构造一个新结点
PNode DCLBuyNode(DataType data)
{
    PNode pNewNode = (PNode)malloc(sizeof(Node));
    if (NULL == PNewNode)
        assert(0);
    pNewNode->_data = data;
    pNewNode->_pNext = NULL;
    pNewNode->_pPre = NULL;
    return pNewNode;
}

//尾插
void DCLPushBack(PNode pHead, DataType data)
{
    PNode DCLBuyNode(data);
    PNode pTailNode = NULL;
    assert(pHead);
    pTailNode = pHead->_pPre;
    pTailNode->_pNext = pNewNode;
    pNewNode->_pPre = pTailNode;
    pNewNode->_pNext = pHead;
    pHead->_pPre = pTailNode;
}

//尾删
void DCLPopBack(PNode pHead)
{
    if (pHead->_pNext == pHead)
    {
        return;
    }
    else
    {
        PNode pPreTail = pHead->_pPre->_pPre;
        free(pPreTail->_pNext);
        pPreTail->_pNext = pHead;
        pHead->_pPre = pPreTail;
    }
}

//头插
void DCLPushFront(PNode pHead, DataType data)
{
    PNode pNewNode = DCLBuyNode(data);
    assert(pHead);
    pNewNode->_pNext = pHead->_pNext;
    pHead->_pNext->_pPre = pNewNode;
    pNewNode->_pPre = pHead;
    pHead->_pNext = pNewNode;
}

//头删
void DCLPopFront(PNode pHead)
{
    if (pHead->_pNext == pHead)
    {
        return;
    }
    else
    {
        PNode pDel = pHead->_pNext;
        pHead->_pNext = pDel->_pNext;
        pDel->_pNext->_pPre = pHead;
        free(pDel);
    }
}

//打印
void DCLPrintList(PNode pHead)
{
    pNode pCur = NULL;
    assert(pHead);
    pCur = pHead->_pNext;
    while (pCur != pHead)
    {
        printf("%d->",pCur->_data);
    }
    printf("\n");
}

//任意位置删除
void DCLInsert(PNode pos, DataType data)
{
    PNode pNewNode = DCLBuyNode(data);
    assert(pNewNode);
    pNewNode->_pNext = pos;
    pos->_pPre->_pNext = pNewNode;
    pNewNode->_pPre = pos->_pPre;
    pos->_pPre = pNewNode;
}

//任意位置删除
void DCLErase(PNode pos)
{
    pos->_pPre->_pNext = pos->_pNext;
    pos->_pNext->_pPre = pos->_pPre;
    free(pos);
}

//查找元素
PNode DCLFind(PNode pHead, DataType data)
{
    PNode pCur = pHead->_pNext;
    while (pCur != pHead)
    {
        if (pCur->_data == data)
        {
            return pCur;
        }
        pCur = pCur->_pNext;
    }
    return NULL;
}

//销毁链表
void DCLDestroy(PNode* ppHead)
{
    PNode pCur = NULL;
    assert(ppHead);
    pCur = (*ppHead)->_pNext;
    while (pCur != *ppHead)
    {
        pCur = pCur->_pNext;
        free(pCur->_pPre);
    }
    free(pCur);
    *ppHead = NULL;
}

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