链表倒数第k个节点

笔试面试——23 输出链表倒数第k个节点

题目分析：设置两个指针，第一个ahead先走k-1步，然后一起遍历，直到链表末尾。

注意特殊情况：

1.头结点为空

2,k值大于总共链表长度

3.k=0

#include "stdafx.h"
#include
using namespace std;

struct ListNode{
	int data;
	ListNode* pNext;
};

//创建链表
void CreatList(ListNode* &pHead,int data)
{
	ListNode* pNewNode = new ListNode();//新建存放数据的节点
	pNewNode->pNext = NULL;
	pNewNode->data = data;
	if(NULL == pHead)
	{
		pHead = pNewNode;
	}
	else
	{
		ListNode* pNode = pHead;//新建遍历节点
		while(pNode->pNext != NULL)
			pNode = pNode->pNext;

		pNode->pNext = pNewNode;
	}	
}


ListNode* FindKthToTail(ListNode* pHead, int k)
{
	if(NULL == pHead || k == 0)
		return NULL;

	ListNode* pAhead = pHead;
	ListNode* pBehind = pHead;

	for(int i = 0;i != k-1;i++)//第一个指针先走k步
	{
		if(pAhead->pNext != NULL)
			pAhead = pAhead->pNext;
		else
			return NULL;
	}
	while(pAhead->pNext != NULL)
	{
		pAhead = pAhead->pNext;
		pBehind = pBehind->pNext;

	}
	return pBehind;
}

int _tmain(int argc, _TCHAR* argv[])
{
	int num = 0;
	int k = 0;
	ListNode* pHead = NULL;
	cout << "请输入要查找倒数第几个节点：" << endl;
	cin >> k;

	cout << "请输入链表" << endl;
	while(cin >> num)
		{
			CreatList(pHead,num);
		}
	
	cout << FindKthToTail(pHead,k)->data << endl;
	system("pause");

	return 0;
}