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#ifndef _DBLINK_H#define _DBLINK_Htemplate<typename Type>class DBLink{public:DBLink() {Init();}DBLink(const DBLink &link) {Init();operator=(link);}const DBLink& operator= (const DBLink &link){if (this != &link){Clear();for (Const_Iterator it = link.Begin(); it != link.End(); it++){push_back(*it);}}return (*this);}public:void Reserve(){Node *pNodeTemp = m_pFirst;while(pNodeTemp != NULL){ Node *pTemppPrev = pNodeTemp->pPrev;pNodeTemp->pPrev = pNodeTemp->pNext;pNodeTemp->pNext = pTemppPrev;pNodeTemp = pNodeTemp->pPrev;}pNodeTemp = m_pFirst;m_pFirst = m_pEnd;m_pEnd = pNodeTemp;}void push_back(const Type& tValue){m_pEnd->pPrev = m_pEnd->pPrev->pNext = new Node(tValue, m_pEnd->pPrev, m_pEnd);m_iLen++;}void pop_back(){Erase(--End());}~DBLink(){Clear();delete m_pFirst;delete m_pEnd;}public:void Clear(){while(m_iLen){pop_back();}}private:typedef struct _Node{Type   tData;_Node *pPrev;_Node *pNext;_Node(const Type& t = Type(), _Node *p = NULL, _Node *n = NULL) :                        tData(t), pPrev(p), pNext(n){}}Node;public:class Const_Iterator{public:Const_Iterator() : m_pNode(NULL){}explicit Const_Iterator(Node *pNode) : m_pNode(pNode){}public:const Type& operator*() const{return m_pNode->tData;}bool operator==(const Const_Iterator &it){return (it.m_pNode == m_pNode);}bool operator!=(const Const_Iterator &it){return !(*this == it);}const Const_Iterator & operator++(){m_pNode = m_pNode->pNext;return (*this);}const Const_Iterator  operator++(int){Const_Iterator old = *this;++(*this);return old;}protected:Node *m_pNode;};class Iterator : public Const_Iterator{public:friend DBLink<typename Type>;Iterator(){}Type& operator*() {return m_pNode->tData;}const Type& operator*() const{return m_pNode->tData;}explicit Iterator(Node *pNode) : Const_Iterator(pNode){}Iterator& operator++(){m_pNode = m_pNode->pNext;return (*this);}Iterator operator++(int){Iterator old(m_pNode);++(*this);return old;}Iterator& operator--(){m_pNode = m_pNode->pPrev;return (*this);}};public:const Const_Iterator Begin() const{return Const_Iterator(m_pFirst->pNext);}const Const_Iterator End() const {return Const_Iterator(m_pEnd);}Iterator Begin(){return Iterator(m_pFirst->pNext);}Iterator End(){return Iterator(m_pEnd);}Iterator Erase(Iterator it){Node *p = it.m_pNode;Iterator retval(p->pNext);p->pPrev->pNext = p->pNext;p->pNext->pPrev = p->pPrev;delete p;m_iLen--;return retval;}private:void Init(){m_pFirst = new Node();m_pEnd = new Node();m_pFirst->pNext = m_pEnd;m_pEnd->pPrev = m_pFirst;m_iLen = 0;}private:Node *m_pFirst;Node *m_pEnd;int m_iLen;};#endif