查找链表倒数第k个数

题目：输入一个单向链表，输出该链表中倒数第k个结点。链表的倒数第0个结点为链表的尾指针。

链表结点定义如下：

struct ListNode
{
    int m_nKey;
    ListNode* m_pNext;
};

答：

#include "stdafx.h"
#include <iostream>
#include <fstream>

using namespace std;

struct ListNode
{
    int m_nKey;
    ListNode* m_pNext;
};

//构造链表
void CreateList(ListNode *&pHead)
{
    fstream fin("list.txt");
    ListNode *pNode = NULL;
    ListNode *pTmp = NULL;
    int data;
    fin>>data;
    while (data)
    {
        pNode = new ListNode;
        pNode->m_nKey = data;
        pNode->m_pNext = NULL;
        if (NULL == pHead)
        {
            pHead = pNode;
            pTmp = pNode;
        }
        else
        {
            pTmp->m_pNext = pNode;
            pTmp = pNode;
        }

        fin>>data;
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    ListNode *pHead = NULL;
    CreateList(pHead);
    ListNode *p = pHead;
    ListNode *q = pHead;
    int k = 5;
    for (int i = 0 ; NULL != p && i < k; i++)
    {
        p = p->m_pNext;
    }
    if (NULL == p)
    {
        return;
    }
    while (NULL != p)
    {
        p = p->m_pNext;
        q = q->m_pNext;
    }
    cout<<q->m_nKey<<endl;
    cout<<endl;
    return 0;
}

运行界面如下：

建造链表的list.txt文件如下：

12 11 10 9 8 7 6 5 4 3 2 1 0