迭代器模板二叉树

Question

我写的二叉树的模板类：

template <class T> 
class Tree { 
public: 
    Tree():head_(NULL),size_(0){} 
    ~Tree(); 
    bool isEmpty()const {return size_ == 0;}; 
    bool insert(const T& ele); 
    bool remove(const T& ele); 
    size_t size() {return size_;} 
public: 

    class inorder_iterator 
    { 
     inorder_iterator& operator++(); 
    private: 
     Node<T>* cur_; 
    }; 
} 

什么是运营商把定义++（我不能老是编译使用以下）

template <class T> 
Tree<T>::inorder_iterator& 
Tree<T>::inorder_iterator::operator++() 
{ 
    //.... 
} 

Answer 1

随着这些变化？它编译：

template <class T> 
class Node {}; 

template <class T> 
class Tree { 
    Node<T> head_; 
    size_t size_; 
public: 
    Tree():head_(NULL),size_(0){} 
    ~Tree(); 
    bool isEmpty()const {return size_ == 0;}; 
    bool insert(const T& ele); 
    bool remove(const T& ele); 
    size_t size() {return size_;} 
public: 

    class inorder_iterator 
    { 
     inorder_iterator& operator++(); 
    private: 
     Node<T>* cur_; 
    }; 
}; 

template <class T> 
typename Tree<T>::inorder_iterator& 
Tree<T>::inorder_iterator::operator++() 
{ 
    //.... 
}