C++ 双向链表

 

数据结构是学习C/C++，继指针后的最大难关之一。这一关的核心是链表。链表是使用最广泛的数据结构，可以说它是你学习计算机进入中级水平的敲门砖！本文提供完整的双向链表代码，虽然只有区区几页，确值得你把每一行都深刻在心中！希望初学者化一周时间(当然你得已经可以无困难的理解指针)，把它滚瓜烂熟，达到能给别人讲的地步！此代码来自VC5带的SDK的DirectX的例子，在 VCSAMPLES\SDK\DIRECTX\INCLUDE和VCSAMPLES\SDK\DIRECTX\CGUTILview plaincopy to clipboardprint?//| File:    linklist.h     #ifndef _LINKLIST_H     #define _LINKLIST_H     typedef struct _NODE  {        struct _NODE    *pPrev;        struct _NODE    *pNext;        void  *pData;    } NODE,  *LPNODE;    class CLinkedList {    private:        LPNODE   Find(void  *pData);        LPNODE   pHead;        LPNODE   pTail;        LPNODE   pCurPosition;    public:        CLinkedList();        ~CLinkedList();        void *GetFirst();        void *GetLast();        void *GetNext();        void *GetNext(void  *pData);        void *GetPrev();        void *GetPrev(void  *pData);        void Add(void  *pData);        void Insert(void  *pData);        void Insert(void *pData, void  *pBefore);        void Append(void  *pData);        void Remove();        void Remove(void  *pData);        void *RemoveFirst();        void *RemoveLast();    };    #define LinkedList  CLinkedList     #endif  //| File:    linklist.h  #ifndef _LINKLIST_H  #define _LINKLIST_H  typedef struct _NODE{  struct _NODE    *pPrev;  struct _NODE    *pNext;  void  *pData;  } NODE,  *LPNODE;  class CLinkedList {  private:  LPNODE   Find(void  *pData);  LPNODE   pHead;  LPNODE   pTail;  LPNODE   pCurPosition;  public:  CLinkedList();  ~CLinkedList();  void *GetFirst();  void *GetLast();  void *GetNext();  void *GetNext(void  *pData);  void *GetPrev();  void *GetPrev(void  *pData);  void Add(void  *pData);  void Insert(void  *pData);  void Insert(void *pData, void  *pBefore);  void Append(void  *pData);  void Remove();  void Remove(void  *pData);  void *RemoveFirst();  void *RemoveLast();  };  #define LinkedList  CLinkedList  #endif view plaincopy to clipboardprint?//| File:    linklist.cpp = a doubly linked list.     #include "linklist.h"     #define NULL  0L     CLinkedList::CLinkedList()  // CLinkedList constructor     {        pHead = pTail = pCurPosition = NULL;    }    CLinkedList::~CLinkedList()//  CLinkedList destructor - free each node     {        LPNODE  pCur, pNext;        pCur = pHead;        pHead = pTail = pCurPosition = NULL;        // Go thru list and free each node         while (pCur != NULL)        {            pNext = pCur->pNext;            delete(pCur);            pCur = pNext;        }    }      //  GetFirst - return app data for first entry in list and make it the current node.     void  * CLinkedList::GetFirst()    {        pCurPosition = pHead;        if (pCurPosition == NULL)        {            return(NULL);        }        return(pCurPosition->pData);    }    // GetLast - return app data to last entry in list and make it the current node.     void  * CLinkedList::GetLast()    {        pCurPosition = pTail;        if (pCurPosition == NULL)        {            return(NULL);        }        return(pCurPosition->pData);    }    // GetNext - return next app data entry in list and make it the current node.     void  * CLinkedList::GetNext()    {        LPNODE  pNext;        // check for empty list or already at end of list.         if ((pCurPosition == NULL) || (pCurPosition->pNext == NULL))        {            return(NULL);        }        pNext = pCurPosition->pNext;        pCurPosition = pNext;        return(pNext->pData);    }    //  GetFirst - return app data that follows a given entry and make it the current node.     void  * CLinkedList::GetNext(void  *pData)    {        pCurPosition = Find(pData);        return(GetNext());    }    // GetPrev - return app data for previous entry in list and make it the current node.     void  * CLinkedList::GetPrev()    {        LPNODE  pPrev;        // check for empty list or already at start         if ((pCurPosition == NULL) || (pCurPosition->pPrev == NULL))        {            return(NULL);        }        pPrev = pCurPosition->pPrev;        pCurPosition = pPrev;        return(pPrev->pData);          }    //  GetFirst - return app data that preceeds a given entry and make it the current node.     void  * CLinkedList::GetPrev(void  *pData)    {        pCurPosition = Find(pData);        return(GetPrev());    }    //  Add - create a new node and put it at the start of the list and make it the current node.     void CLinkedList::Add(void  *pData)    {        LPNODE  pNew = new NODE;        // setup node and prepare it for its role as the new head of the list         pNew->pData = pData;        pNew->pNext = pHead;        pNew->pPrev = NULL;        // The old head of list (if any) should point to new node)         if (pHead != NULL)            pHead->pPrev = pNew;        // Make new node the head and current position         pHead = pNew;        pCurPosition = pNew;        // Check to see if new node is also the tail (ie. only list entry)         if (pTail == NULL)            pTail = pNew;    }    //  Append - create a new node and put it at the end of the list.     void CLinkedList::Append(void  *pData)    {        LPNODE  pNew = new NODE;        // setup node and prepare it for its role as the new tail of the list         pNew->pData = pData;        pNew->pPrev = pTail;        pNew->pNext = NULL;        // The old tail of list (if any) should point to new node.         if (pTail != NULL)            pTail->pNext = pNew;        // Make new node the tail         pTail = pNew;        // Check to see if new node is also the head (ie. only list entry)         if (pHead == NULL)        {            pHead = pNew;            pCurPosition = pNew;        }    }    //  Find - private method to find the node with the specified app data attached to it.     LPNODE CLinkedList::Find(void  *pData)    {        LPNODE pCur;        // go thru list until we reach end or we find the right node.         for (pCur=pHead; (pCur != NULL) && (pCur->pData != pData); pCur= pCur->pNext);        return(pCur);    }    //  Insert - create a new node and put it in front of the current position node and make it the current position.     void CLinkedList::Insert(void  *pData)    {        LPNODE  pNext, pPrev;        LPNODE  pNew = new NODE;        pNew->pData = pData;        // check to be sure that there is a current node         if (pCurPosition != NULL)        {                      // get pointers of current position             pPrev = pCurPosition->pPrev;            pNext = pCurPosition->pNext;            // set new nodes pointers for insertion into the list             pNew->pPrev = pPrev;            pNew->pNext = pCurPosition;            // Set the node in front of new node (if any) to point to it             if (pPrev != NULL)            {                pPrev->pNext = pNew;                // No node in front -> new node is at head             } else {                pHead = pNew;            }            // make new node the current node             pCurPosition = pNew;            // No current node, just Add to front         } else {            Add(pData);        }    }    //  Insert - create a new node and put it in front of the specified node and make it the current position.     void CLinkedList::Insert(void *pData, void  *pBefore)    {        // simply make the specified node current and insert the new         // node.         pCurPosition = Find(pBefore);        Insert(pData);    }      //  Remove - remove a specified node from the list.     //  Note: we do not delete the app data attached to the node!     void CLinkedList::Remove()    {        LPNODE  pCur, pNext, pPrev;        pCur = pCurPosition;        if (pCur != NULL)        {            // save a copy of the links             pPrev = pCur->pPrev;            pNext = pCur->pNext;            // Is there a node ahead of us?             if (pPrev != NULL)            {                // yes -> update it to not point to us.                 pPrev->pNext = pNext;            } else {                // no -> update head to not point to us.                 pHead = pNext;                pCurPosition = pNext;            }            // Is there a node behind us?             if (pNext != NULL)            {                // yes -> update it to not point to us.                 pNext->pPrev = pPrev;                pCurPosition = pNext;            } else {                // no -> update tail to not point to us.                 pTail = pPrev;                pCurPosition = pPrev;            }            delete(pCur);        }    }      //  Remove - remove a specified node from the list.     //  Note: we do not delete the app data attached to the node!     void CLinkedList::Remove(void  *pData)    {        pCurPosition = Find(pData);        Remove();    }      //  RemoveFirst - remove the first node in the list and return the app data associated with it.     void * CLinkedList::RemoveFirst()    {        LPNODE  pCur, pNext;        void  *pData = NULL;        pCur = pHead;        // is there a node at the head?         if (pCur != NULL)        {            // take first node out of list.             pNext = pCur->pNext;            pHead = pNext;            pCurPosition = pNext;            // are there any nodes after us?             if (pNext != NULL)            {                // yes -> make it the new head                 pNext->pPrev = NULL;            } else {                // no -> the list is now empty                 pTail = NULL;            }            // get app data for node and then delete it             pData = pCur->pData;            delete(pCur);        }        return(pData);    }    //  RemoveLast - remove the last node in the list and return the app data associated with it.     void * CLinkedList::RemoveLast()    {        LPNODE  pCur, pPrev;        void  *pData = NULL;        pCur = pTail;        // is there a node at the tail?         if (pCur != NULL)        {            // take last node out of list.             pPrev = pCur->pPrev;            pTail = pPrev;            // are there any nodes ahead of us?             if (pPrev != NULL)            {                // yes -> make it the new tail node                 pPrev->pNext = NULL;            } else {                // no -> list is now empty                 pHead = NULL;                pCurPosition = NULL;            }            // get app data for node and then delete it             pData = pCur->pData;            delete(pCur);        }        return(pData);    }