查找单链表的倒数第k个节点，要求只能遍历一次链表

#include "LinkList.h"
#include <assert.h>
#include <stdio.h>

// 在单链表的尾部插入一个节点
void PushBack(PNode* pHead, DataType data)
{
PNode pCurNode = NULL;
PNode pNewNode = NULL;
assert(pHead);
pNewNode = BuyNode(data);
if(pNewNode == NULL)
return;
if(*pHead == NULL)
{
*pHead = pNewNode;
}
else
{
pCurNode = *pHead;
while(pCurNode->_pNext)
{
pCurNode = pCurNode->_pNext;
}
pCurNode->_pNext = pNewNode;
}
}
// 构建一个新节点
Node* BuyNode(DataType data)
{
PNode pNewNode = (Node*)malloc(sizeof(Node));
if(pNewNode == NULL)
return NULL;
pNewNode->_data = data;
pNewNode->_pNext = NULL;
return pNewNode;
}

// 正向打印单链表
void PrintList(PNode pHead)
{
if(pHead == NULL)
return;
while(pHead)
{
printf("%d->",pHead->_data);
pHead = pHead->_pNext;
}
printf("NULL\n");
}

// 查找单链表的倒数第K个结点，要求只遍历一次链表
PNode FindLastKNode(PNode pHead, size_t k)
{
PNode pFastNode = NULL;
PNode pSlowNode = NULL;
if(pHead == NULL)
return NULL;
pSlowNode = pHead;
pFastNode = pHead;
while(--k)
{
pFastNode = pFastNode->_pNext;
if(pFastNode == NULL)
return NULL;
}
while(pFastNode->_pNext)
{
pSlowNode = pSlowNode->_pNext;
pFastNode = pFastNode->_pNext;
}
return pSlowNode;
}

//销毁单链表，释放空间
void DestroyList(Node* pHead)
{
while(pHead)
{
Node* temp = pHead;
pHead = pHead->_pNext;
free(temp);
}
}

#include "LinkList.h"
void test()
{
PNode node = NULL;
PushBack(&node,1);
PushBack(&node,3);
PushBack(&node,5);
PushBack(&node,4);
PushBack(&node,2);
PushBack(&node,6);
PrintList(node);
node = FindLastKNode(node,3);
printf("从倒数第k个结点开始的链表：\n");
PrintList(node);
DestroyList(node);
}
int main()
{
test();
return 0;
}