输入一个单向链表，输出该链表中倒数第K个结点

http://blog.csdn.net/itcastcpp/article/details/39274891

//尹成 单链表操作#include <iostream>using namespace std;class LinkList;struct LinkNode{public:LinkNode(int value =0):m_value(value),pNext(NULL){}~LinkNode(){pNext = NULL;}friend class LinkList;int m_value;LinkNode* pNext;};//带头结点的链表class LinkList{public:LinkList();~LinkList();void Insert(int data);void Delete(int data);void Sort();bool IsEmpty();void Reverse();void Destroy();int Length();LinkNode* Find(int data);bool IsLoop();void Print();LinkNode* FindIndex(int index);//使用下标LinkNode* FindLastNum(int n);//使用两个指针private:LinkNode* pHead;};LinkList::LinkList(){pHead = new LinkNode();}LinkList::~LinkList(){Destroy();}//从大到小插入void LinkList::Insert(int data){if(NULL == pHead){cout<<"料表未创建"<<endl;return;}LinkNode* pCur = pHead;//移动到待插入节点的前一个节点while(pCur->pNext != NULL){if(pCur->pNext->m_value < data)break;pCur = pCur->pNext;}LinkNode* pTmp = new LinkNode(data);pTmp->pNext = pCur->pNext;pCur->pNext = pTmp;}void LinkList::Delete(int data){if(NULL == pHead){cout<<"链表未创建"<<endl;return;}if(NULL == pHead->pNext){cout<<"链表为空"<<endl;return;}LinkNode* pCur = pHead;while(pCur->pNext){//指向要删除节点的前一个节点if(pCur->pNext->m_value == data){LinkNode* pDel = pCur->pNext;pCur->pNext = pCur->pNext->pNext;pDel = NULL;delete pDel;}elsepCur = pCur->pNext;}}//从小到大排序void LinkList::Sort(){if(pHead == NULL){cout<<"链表未创建"<<endl;return;}if(pHead->pNext == NULL){cout<<"链表为空"<<endl;return;}LinkNode* pCur = pHead;LinkNode* pNewHead = new LinkNode();while(pCur){LinkNode * pTmp = pCur;pCur = pCur->pNext;LinkNode* p = pNewHead;//将pTmp插入到新的链表中 插入时候按照从小到大顺序while(p->pNext){if(p->pNext->m_value > pTmp->m_value){break;}p = p->pNext;}if(pTmp != pHead){pTmp->pNext = p->pNext;p->pNext = pTmp;}//delete pHead;//释放掉原来的内存  这里不注释掉 导致二次释放指针？pHead = pNewHead;}}bool LinkList::IsEmpty(){if(NULL == pHead){cout<<"链表未创建"<<endl;return false;}return pHead->pNext == NULL;}int LinkList::Length(){if(NULL == pHead){cout<<"链表未创建"<<endl;return 0;}int nLength = 0;LinkNode* pCur = pHead->pNext;while(pCur){nLength++;pCur=pCur->pNext;}return nLength;}void LinkList::Reverse(){if(NULL == pHead){cout<<"链表未创建"<<endl;return;}if(pHead->pNext == NULL){cout<<"链表为空"<<endl;return;}else{LinkNode* pCur = pHead->pNext->pNext;LinkNode* pPre = pHead->pNext;LinkNode* pnext = NULL;while(pCur){pnext = pCur->pNext;pCur->pNext = pPre;pPre = pCur;pCur = pnext;}pHead->pNext->pNext =NULL;pHead->pNext = pPre;}}void LinkList::Destroy(){if(pHead == NULL){cout<<"链表未创建"<<endl;return;}while(pHead->pNext){LinkNode* pDel = pHead->pNext;pHead->pNext = pDel->pNext;delete pDel;pDel = NULL;}delete pHead;pHead = NULL;}LinkNode* LinkList::Find(int data){if(NULL == pHead){cout<<"链表未创建"<<endl;return NULL;}if(NULL == pHead->pNext){cout<<"链表为空"<<endl;return NULL;}LinkNode* pCur = pHead->pNext;while(pCur){if(pCur->m_value == data)return pCur;pCur= pCur->pNext;}return NULL;}void LinkList::Print(){if(NULL == pHead){cout<<"链表未创建"<<endl;return;}if(NULL == pHead->pNext){cout<<"链表为空"<<endl;return;}else{LinkNode* pCur = pHead->pNext;while(pCur){cout<<pCur->m_value<<" ";pCur = pCur->pNext;}cout<<endl;}}bool LinkList::IsLoop(){if(NULL == pHead){cout<<"链表未创建"<<endl;return false;}if(NULL == pHead->pNext){cout<<"链表为空"<<endl;return false;}LinkNode* pFast = pHead->pNext;LinkNode* pLow = pHead->pNext;//pFast->pNext != NULL 这个条件是很关键的while(pFast != NULL &&pLow != NULL && pFast->pNext !=NULL){pFast = pFast->pNext->pNext;pLow = pLow->pNext;if(pFast == pLow)return true;}return false;}//返回倒数第n个节点LinkNode* LinkList::FindIndex(int n){if(n <= 0 || n > Length())return NULL;LinkNode* pCur = pHead->pNext;for(int i = 1;i < n;i++){pCur = pCur->pNext;}return pCur;}//这一种方法利用了中间间隔LinkNode* LinkList::FindLastNum(int n){if(pHead == NULL || pHead->pNext == NULL||n < 0)return NULL;LinkNode* pCur = pHead->pNext;LinkNode* pFirst = pHead->pNext;while(n > 0){pFirst = pFirst->pNext;if(NULL == pFirst)return NULL;n--;}while(pFirst->pNext){pFirst = pFirst->pNext;pCur = pCur->pNext;}return pCur;}int main(){LinkList list;      list.Insert(12);      list.Insert(14);      list.Insert(2);      list.Insert(122);      list.Insert(5);      list.Insert(4);      list.Insert(7);      list.Print();      int k;      cout << "请输入要查询倒数第几个结点(计数从0开始):";      cin >> k;      LinkNode *p = list.FindIndex(list.Length() - k);      if (p)      {          cout << p->m_value << endl;      }      LinkNode *p2 = list.FindLastNum(k);      if (p2)      {          cout << p2->m_value << endl;      }cout<<"链表进行排序之后的结果:"<<endl;list.Sort();list.Print();return 0;}