双向链表描述

//双向链表的类定义
template<class T>
class DoubleNode{
    friend Double<T>;
    private:
        T data;
        DoubleNode<T> *left,*right;
};

template<class T>
class Double{
    public:
        Double() {LeftEnd = RightEnd = 0;}
        ~Double();
        int Length() const;
        bool Find(int k, T & x) const;
        int Search(const T & x) const;
        Double<T> Delete(int k,const T & x);
        Double<T> & Insert(int k, const T & x);
        void Outpub(ostream & out) const;
    private:
        DoubleNode<T> *LeftEnd,*RightEnd;
};