单链表逆序

复习下单链表的逆置，留作后看：

先上张图，便于理解代码：

代码贴上：

/************************************************************************/
/* create by leisc    2014.07.11                                           */
/************************************************************************/

#include <iostream>
using namespace std;

typedef struct _listnode
{
    int data;
    _listnode *pNext;
}LISTNODE;

//打印链表
int printlist(const LISTNODE *head)
{
    int ret = 0;
    if (head == NULL)
    {
        ret = -1;
        return ret;
    }
    cout << endl;
    for (LISTNODE *tmp = (LISTNODE*)head->pNext; tmp != NULL; tmp = tmp->pNext)
    {
        printf("%d ", tmp->data);
    }
    cout << endl;
    return ret;
}

int CreateAndIniList(LISTNODE ** list)
{
    int n = 1;//记录链表元素数量
    int cdata = 0;//链表元素数据存储
    int ret = 0;

    LISTNODE *pHead = NULL;
    LISTNODE *pTmp = NULL;
    LISTNODE *pCur = NULL;
    //c写法创建新节点
    //pPri = pCur = (LISTNODE *)malloc(sizeof(LISTNODE));
    pHead = pCur = new LISTNODE;
    if (pCur == NULL || pHead == NULL)
    {
        ret = -1;
        return ret;
    }

    //头节点初始化
    pHead->data = 0;
    pHead->pNext = NULL;
    pCur = pHead;

    cout << "Please enter the data you want to insert into the list(enter -1 to end!):" << endl;
    cout << "The " << n << "'th node data:";
    cin >> cdata;
    //循环添加链表元素，采用尾插法
    while (cdata != -1)
    {
        pTmp = new LISTNODE;

        pTmp->data = cdata;

        pTmp->pNext = NULL;

        pCur->pNext = pTmp;
        pCur = pTmp;
        n++;
        cout << "The" << n << "'th node data:";
        cin >> cdata;
    }

    *list = pHead;
    return ret;
}

int ReverseList(LISTNODE **list)
{
    if (list == nullptr)//判断是否是空链表
    {
        return -1;
    }

    //申请新节点，将入参接过来
    LISTNODE* reList = new LISTNODE;
    reList = *list;

    //判断是否是空链表或者只有一个元素
    if (reList->pNext == nullptr ||reList->pNext->pNext == nullptr)
    {
        return -1;
    }
    
    //采用双节点跳马式循环修改指针指向
    LISTNODE* pPre = nullptr;    //指向前面一个节点
    LISTNODE* pCur = nullptr;    //指向后面一个节点

    pPre = reList->pNext;        //将pPre指向第一个节点
    pCur = pPre->pNext;            //将pCur指向第二个节点
    //reList->pNext = nullptr;    //这里可以将头节点指空，当然就那么放着也行
    pPre->pNext = nullptr;        //首先需要把第一个节点的的指向赋空，要不然就死循环了
    LISTNODE* pTemp = nullptr;    //申请一个缓存指针，用于存储向后的节点地址

    //循环进行指针逆置
    while (pCur)
    {
        pTemp = pCur->pNext;//将pCur的下一个地址缓存起来
        pCur->pNext = pPre; //将pCur的下一个指向他的前一个，即pPre
        //两个指针同时向后跳一
        pPre = pCur;
        pCur = pTemp;
    }

    //最后将头节点指向逆置后的第一个节点，即pPre
    reList->pNext = pPre;

    return 0;
}

int main()
{
    LISTNODE *pHead = NULL;

    CreateAndIniList(&pHead);
    cout << "原始链表：" << endl;
    printlist(pHead);

    ReverseList(&pHead);

    cout << "逆序后的链表" << endl;
    printlist(pHead);

    return 0;
}

运行结果：