// -------------------------------------------------------------------
// TREE NODE CLASS 
template <class T>
class TreeNode {
public:
  TreeNode() : left(NULL), right(NULL)/*, parent(NULL)*/ {}
  TreeNode(const T& init) : value(init), left(NULL), right(NULL)/*, parent(NULL)*/ {}
  T value;
  TreeNode* left;
  TreeNode* right;
  // one way to allow implementation of iterator increment & decrement
  // TreeNode* parent;
};

// -------------------------------------------------------------------
// TREE NODE ITERATOR CLASS
template <class T>
class tree_iterator {
public:
  tree_iterator() : ptr_(NULL) {}
  tree_iterator(TreeNode<T>* p) : ptr_(p) {}
  tree_iterator(const tree_iterator& old) : ptr_(old.ptr_) {}
  ~tree_iterator() {}
  tree_iterator& operator=(const tree_iterator& old) { ptr_ = old.ptr_;  return *this; }
  // operator* gives constant access to the value at the pointer
  const T& operator*() const { return ptr_->value; }
  // comparions operators are straightforward
  bool operator== (const tree_iterator& rgt) { return ptr_ == rgt.ptr_; }
  bool operator!= (const tree_iterator& rgt) { return ptr_ != rgt.ptr_; }
  // increment & decrement operators
  tree_iterator<T> & operator++() { /* discussed & implemented in Lecture 19 */









    return *this;
  }
  tree_iterator<T> operator++(int) {  tree_iterator<T> temp(*this);  ++(*this);  return temp;  }
  tree_iterator<T> & operator--() { /* implementation omitted */ }
  tree_iterator<T> operator--(int) {  tree_iterator<T> temp(*this);  --(*this);  return temp;  }

private:
  // representation
  TreeNode<T>* ptr_;
};

// -------------------------------------------------------------------
// DS_SET CLASS
template <class T>
class ds_set {
public:
  ds_set() : root_(NULL), size_(0) {}
  ds_set(const ds_set<T>& old) : size_(old.size_) { root_ = this->copy_tree(old.root_,NULL); }
  ~ds_set() { this->destroy_tree(root_); root_ = NULL; }
  ds_set& operator=(const ds_set<T>& old) { /* implementation omitted */ }

  typedef tree_iterator<T> iterator;

  int size() const { return size_; }
  bool operator==(const ds_set<T>& old) const { return (old.root_ == this->root_); }

  // FIND, INSERT & ERASE
  iterator find(const T& key_value) { return find(key_value, root_); }
  std::pair< iterator, bool > insert(T const& key_value) { return insert(key_value, root_); }
  int erase(T const& key_value) { return erase(key_value, root_); }

  // OUTPUT & PRINTING
  friend std::ostream& operator<< (std::ostream& ostr, const ds_set<T>& s) {
    s.print_in_order(ostr, s.root_);
    return ostr;
  }
 
  // ITERATORS
  iterator begin() const { 
    if (!root_) return iterator(NULL);
    TreeNode<T>* p = root_;
    while (p->left) p = p->left;
    return iterator(p);
  }
  iterator end() const { return iterator(NULL); }

private:
  // REPRESENTATION
  TreeNode<T>* root_;
  int size_;

  // PRIVATE HELPER FUNCTIONS
  TreeNode<T>*  copy_tree(TreeNode<T>* old_root) { /* Implemented in Lab 9 */ }
  void destroy_tree(TreeNode<T>* p) { 
     /* Implemented in Lecture 18 */





  }

  iterator find(const T& key_value, TreeNode<T>* p) {  /* Implemented in Lecture 17 */  }

  std::pair<iterator,bool> insert(const T& key_value, TreeNode<T>*& p) {
    // NOTE: will need revision to support & maintain parent pointers
    if (!p) {
      p = new TreeNode<T>(key_value);
      this->size_++;
      return std::pair<iterator,bool>(iterator(p), true);
    }
    else if (key_value < p->value)
      return insert(key_value, p->left);
    else if (key_value > p->value)
      return insert(key_value, p->right);
    else
      return std::pair<iterator,bool>(iterator(p), false);
  }
  
  int erase(T const& key_value, TreeNode<T>* &p) { /* Implemented in Lecture 19 */ }

  void print_in_order(std::ostream& ostr, const TreeNode<T>* p) const {
    if (p) {
      print_in_order(ostr, p->left);
      ostr << p->value << "\n";
      print_in_order(ostr, p->right);
    }
  }
};