数据结构的一个简单的

#include<iostream.h>
template<class Elem>  
class BinNode { 
public:
    virtual Elem& val( ) =0;
    virtual void setVal( const Elem& ) = 0;
    virtual BinNode* left( ) const = 0;
    virtual void setLeft( BinNode* ) = 0;
    virtual BinNode* right( ) const = 0; 
    virtual void setRight( BinNode* ) = 0;
    virtual bool isLeaf( ) = 0;
};
template <class Elem>
class BinNodePtr : public BinNode<Elem> {
private:
  Elem it;         // The node's value
  BinNodePtr* lc;  // Pointer to left child
  BinNodePtr* rc;  // Pointer to right child
public:
  BinNodePtr() { lc = rc = NULL; }
  BinNodePtr(Elem e, BinNodePtr* l =NULL,BinNodePtr* r =NULL){ it = e; lc = l; rc = r; }
  Elem& val() { return it; }
  void setVal(const Elem& e) { it = e; }
  inline BinNode<Elem>* left() const
    { return lc; }
  void setLeft(BinNode<Elem>* b)
    { lc = (BinNodePtr*)b; }
  inline BinNode<Elem>* right() const
    { return rc; }
  void setRight(BinNode<Elem>* b)