不使用库实现队列的基本操作

template<typenameT>

structNode

{public:

                Node(constT&d)

                                :_data(0)

                                , _next(NULL)

                                , _pre(NULL)

                {  }

                T* _data;

                Node<T>* _next;

                Node<T>* _pre;

};

template<typenameT>

classQueue //先进先出，

{

public:

                Queue()

                                :_tail(NULL)

                                , _head(NULL)

                                , _size(0)

                {  }

                voidPush(constT&n)

                {

                                if(_size == 0)

                                {

                                                _head = _tail = _ByeNode(n);

                                }

                                else

                                {

                                                Node<T> *temp = _ByeNode(n);

                                                _tail->_next = temp;

                                                temp->_pre = _tail;

                                                _tail = _tail->_next;

                                }

                                _size++;

                }

                voidPop()  //移除一个元素,删除队头

                {

                                if(_size == 0)

                                {

                                                return;

                                }

                                elseif(_size = 1)

                                {

                                                delete_head;

                                                _head =NULL;

                                                _tail =NULL;

                                }

                                else

                                {

                                                _head =_head->_next;

                                                delete_head->_pre;

                                }

                                _size--;

                }

                T& Front()  //返回第一个插入的元素,即队头

                {

                                return_head;

                }

                T& Back()  //返回最后被插入的元素，即队尾

                {

                                return_tail;

                }

                boolEmpty() //队列为空时，返回true

                {

                                if(_size == 0)

                                {

                                                returntrue;

                                }

                                else

                                {

                                                returnfalse;

                                }

                }

                size_tSize() //队列中元素个数

                {

                                return_size;

                }

                Node<T> * _ByeNode(constT&n)

                {

                                returnnewNode<T>(n);

                }

protected:

                Node<T>* _tail;

                Node<T>* _head;

                size_t_size;

};