diff --git a/TinySTL/BinarySearchTree.h b/TinySTL/BinarySearchTree.h
index 221fd32..e120dd6 100644
--- a/TinySTL/BinarySearchTree.h
+++ b/TinySTL/BinarySearchTree.h
@@ -2,14 +2,111 @@
 #define _BINARY_SEARCH_TREE_H_
 
 #include "Allocator.h"
+#include "String.h"
 
 namespace TinySTL{
+	namespace {
+		template<class T>
+		class bst_iter;
+	}
 	//class of binary_search_tree
-	template<class T, class Alloc = TinySTL::allocator<T>>
-	class binary_search_tree{};
-	//class of bst iterator
 	template<class T>
-	class bst_iter{};
+	class binary_search_tree{
+	private:
+		template<class T>
+		friend class bst_iter;
+	private:
+		struct node{
+			T data_;
+			node *left_;
+			node *right_;
+		};
+		typedef TinySTL::allocator<node> nodeAllocator;
+	public:
+		typedef T vaule_type;
+		typedef bst_iter<node> iterator;
+		typedef T& reference;
+	private:
+		node *root_;
+	public:
+		binary_search_tree() :root_(0){}
+		binary_search_tree(const binary_search_tree&) = delete;
+		binary_search_tree& operator=(const binary_search_tree&) = delete;
+		~binary_search_tree(){}//TODO
+
+		void insert(const T& val);
+
+		void print_preorder(const string& delim = " ", std::ostream& os = std::cout)const;
+		void print_inorder(const string& delim = " ", std::ostream& os = std::cout)const;
+		void print_postorder(const string& delim = " ", std::ostream& os = std::cout)const;
+	private:
+		void insert_elem(const T& val, node *&ptr);
+		void print_preorder_aux(const string& delim, std::ostream& os, const node *ptr)const;
+		void print_inorder_aux(const string& delim, std::ostream& os, const node *ptr)const;
+		void print_postorder_aux(const string& delim, std::ostream& os, const node *ptr)const;
+	};//end of bst class
+	template<class T>
+	void binary_search_tree<T>::insert_elem(const T& val, node *&ptr){
+		if (ptr == 0){
+			ptr = nodeAllocator::allocate();
+			ptr->data_ = val;
+			ptr->left_ = ptr->right_ = 0;
+		}
+		else{
+			if (val < ptr->data_){
+				return insert_elem(val, ptr->left_);
+			}
+			else if (val > ptr->data_){
+				return insert_elem(val, ptr->right_);
+			}
+		}
+	}
+	template<class T>
+	void binary_search_tree<T>::insert(const T& val){
+		insert_elem(val, root_);
+	}
+	template<class T>
+	void binary_search_tree<T>::print_preorder_aux(const string& delim, std::ostream& os, const node *ptr)const{
+		if (ptr){
+			os << ptr->data_ << delim;
+			print_preorder_aux(delim, os, ptr->left_);
+			print_preorder_aux(delim, os, ptr->right_);
+		}
+	}
+	template<class T>
+	void binary_search_tree<T>::print_preorder(const string& delim, std::ostream& os)const{
+		print_preorder_aux(delim, os, root_);
+	}
+	template<class T>
+	void binary_search_tree<T>::print_inorder_aux(const string& delim, std::ostream& os, const node *ptr)const{
+		if (ptr){
+			print_inorder_aux(delim, os, ptr->left_);
+			os << ptr->data_ << delim;
+			print_inorder_aux(delim, os, ptr->right_);
+		}
+	}
+	template<class T>
+	void binary_search_tree<T>::print_inorder(const string& delim, std::ostream& os)const{
+		print_inorder_aux(delim, os, root_);
+	}
+	template<class T>
+	void binary_search_tree<T>::print_postorder_aux(const string& delim, std::ostream& os, const node *ptr)const{
+		if (ptr){
+			print_postorder_aux(delim, os, ptr->left_);
+			print_postorder_aux(delim, os, ptr->right_);
+			os << ptr->data_ << delim;
+		}
+	}
+	template<class T>
+	void binary_search_tree<T>::print_postorder(const string& delim, std::ostream& os)const{
+		print_postorder_aux(delim, os, root_);
+	}
+
+	namespace{
+		//class of bst iterator
+		template<class T>
+		class bst_iter{};
+	}
 }
 
 #endif
\ No newline at end of file