template <class Type> class ExtBinTree;template <class Type> class Element {  friend class ExtBinTree;  private:    Type data;    Element<Type> *leftChild, *rightChild;  };template <class Type> class ExtBinaryTree {  public:    ExtBinTree ( ExtBinTree<Type> &bt1, ExtBinTree<Type> &bt2 ) {      root->leftChild = bt1.root;      root->rightChild = bt2.root;      root->data.key = bt1.root->data.key + bt2.root->data.key;	}  protected:    const int DefaultSize = 20;    Element<Type> *root;    MinHeap< ExtBinTree<Type> > hp;  }  template <class Type> void HuffmanTree ( Type *fr, int n, ExtBinTree<Type> & newtree ) {    ExtBinTree<Type> & first, & second;    ExtBinTree<Type> Node[DafualtSize];    if ( n > DefaultSize ) {      cerr << "Size n " << n << "exceeds the boundary of Array" << endl;      return;      }    for ( int i=0; i<n; i++ ) {      Node[i].root->data.key = fr[i];      Node[i].root->leftChild = Node[i].root->rightChild = NULL;	}    hp.MinHeap ( Node, n );    for ( int i=0; i<n-1; i++ ) {      hp.RemoveMin ( first );  hp.RemoveMin ( second );      newtree = new ExtBinTree<Type> ( first, second );      hp.Insert ( newtree );      }    return hp.RemoveMin ( newtree );  }