diff --git a/src/11/helloworld/helloworld.cpp b/src/11/helloworld/helloworld.cpp
index f04de7a..06b3d03 100755
--- a/src/11/helloworld/helloworld.cpp
+++ b/src/11/helloworld/helloworld.cpp
@@ -1,4 +1,3 @@
-#include <array>
 #include <cstdint>
 #include <iostream>
 #include <utility>
diff --git a/src/12/c6/BinarySearchTree.hpp b/src/12/c6/BinarySearchTree.hpp
new file mode 100644
index 0000000..9cabfcf
--- /dev/null
+++ b/src/12/c6/BinarySearchTree.hpp
@@ -0,0 +1,112 @@
+#pragma once
+
+#include <ostream>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <type_traits>
+
+namespace zt {
+    template<class T>
+    class BinarySearchTree {
+    public:
+        using valueType = std::remove_cv_t<T>;
+    private:
+        struct Node {
+            valueType val;
+            Node* leftSon{nullptr};
+            Node* rightSon{nullptr};
+        };
+        Node* root{nullptr};
+
+        void _deleteTree(Node* node){
+            if(node == nullptr) return;
+            _deleteTree(node->leftSon);
+            _deleteTree(node->rightSon);
+            delete node;
+        }
+
+        void _inorderTraversal(Node* now, void(*func)(Node* now)) const {
+            if(now->leftSon != nullptr){
+                _inorderTraversal(now->leftSon, func);
+            }
+            func(now);
+            if(now->rightSon != nullptr){
+                _inorderTraversal(now->rightSon, func);
+            }
+        }
+
+        void _toString(const Node* now, std::stringstream& ss) const {
+            if(now->leftSon != nullptr){
+                _toString(now->leftSon, ss);
+            }
+            ss << now->val << ", ";
+            if(now->rightSon != nullptr){
+                _toString(now->rightSon, ss);
+            }
+        }
+
+    public:
+        BinarySearchTree() = default;
+
+        void insert(const valueType& val) {
+            Node* newNode = new Node{};
+            newNode->val=val;
+            if(root == nullptr){
+                root = newNode;
+                return;
+            }
+            Node* current = root;
+            Node* parent = nullptr;
+            while(current != nullptr){
+                parent = current;
+                if(val < current->val){
+                    current = current->leftSon;
+                } else {
+                    current = current->rightSon;
+                }
+            }
+            if(val < parent->val){
+                parent->leftSon = newNode;
+            } else {
+                parent->rightSon = newNode;
+            }
+        }
+
+        valueType findMin() const {
+            if(root == nullptr){
+                throw std::runtime_error("Tree is empty");
+            }
+            Node* current = root;
+            while(current->leftSon != nullptr){
+                current = current->leftSon;
+            }
+            return current->val;
+        }
+
+        valueType findMax() const {
+            if(root == nullptr){
+                throw std::runtime_error("Tree is empty");
+            }
+            Node* current = root;
+            while(current->rightSon != nullptr){
+                current = current->rightSon;
+            }
+            return current->val;
+        }
+
+        std::string toString() const {
+            std::stringstream ss;
+            ss << "{ ";
+            if(root != nullptr){
+                _toString(root, ss);
+            }
+            ss << "}";
+            return ss.str();
+        }
+        
+        ~BinarySearchTree(){
+            _deleteTree(root);
+        }
+    };
+}
diff --git a/src/12/c6/CartesianTree.hpp b/src/12/c6/CartesianTree.hpp
new file mode 100644
index 0000000..61541d1
--- /dev/null
+++ b/src/12/c6/CartesianTree.hpp
@@ -0,0 +1,98 @@
+// #pragma once
+
+// #include <iostream>
+// #include <ostream>
+// #include <sstream>
+// #include <stdexcept>
+// #include <string>
+// #include <type_traits>
+// #include "Stack.hpp"
+
+// namespace zt {
+//     template<class T>
+//     class CartesianTree{
+//     public:
+//         using valueType = std::remove_cv_t<T>;
+//     private:
+//         struct Node{
+//             valueType val;
+//             Node* leftSon{nullptr};
+//             Node* rightSon{nullptr};
+//         };
+//         Stack<Node*> stack;
+//         Node* root{nullptr};
+//         void _dfs(Node *now,void(*func)(Node* now)){
+//             if(now->leftSon!=nullptr){
+//                 _dfs(now->leftSon, func);
+//             }
+//             if(now->rightSon!=nullptr){
+//                 _dfs(now->rightSon, func);
+//             }
+//             func(now);
+//         }
+//         void _dfs(const Node *const now,void(*func)(Node*const now))const{
+//             if(now->leftSon!=nullptr){
+//                 _dfs(now->leftSon, func);
+//             }
+//             if(now->rightSon!=nullptr){
+//                 _dfs(now->rightSon, func);
+//             }
+//             func(now);
+//         }
+//         void _toString(const Node*const now,std::stringstream&ss)const{
+//             if(now->leftSon!=nullptr){
+//                 _toString(now->leftSon, ss);
+//             }
+//             ss<<now->val<<", ";
+//             if(now->rightSon!=nullptr){
+//                 _toString(now->rightSon, ss);
+//             }
+//         }
+//         void dfs(void(*func)(Node*const now))const{
+//             if(root!=nullptr){
+//                 _dfs(root,func);
+//             }
+//         }
+//         void dfs(void(*func)(Node* now)){
+//             if(root!=nullptr){
+//                 _dfs(root,func);
+//             }
+//         }
+//     public:
+//         constexpr explicit CartesianTree(){}
+//         constexpr void insert(valueType const& val){
+//             Node *const newNode {new Node{}};
+//             newNode->val=val;
+//             while(!stack.empty()&&val<stack.top()->val){
+//                 newNode->leftSon=stack.top();
+//                 stack.pop();
+//             }
+//             if(!stack.empty()){
+//                 stack.top()->rightSon=newNode;
+//             }else{
+//                 root = newNode;
+//             }
+//             stack.push(newNode);
+//         }
+//         constexpr valueType top()const{
+//             if(root==nullptr){
+//                 throw std::runtime_error("the root of the Cartesian is nullptr");
+//             }
+//             return root->val;
+//         }
+//         ~CartesianTree(){
+//             dfs([](Node* now){
+//                 delete now;
+//             });
+//         }
+//         std::string toString()const{
+//             std::stringstream ss;
+//             ss<<"{ ";
+//             if(root!=nullptr){
+//                 _toString(root, ss);
+//             }
+//             ss<<" }";
+//             return std::string(ss.str());
+//         }
+//     };
+// }
\ No newline at end of file
diff --git a/src/12/c6/Stack.hpp b/src/12/c6/Stack.hpp
new file mode 100644
index 0000000..07f7924
--- /dev/null
+++ b/src/12/c6/Stack.hpp
@@ -0,0 +1,59 @@
+#pragma once
+
+#include <cstddef>
+#include <stdexcept>
+#include <type_traits>
+namespace zt {
+    template<class T>
+    class Stack{
+    private:
+        using valueType = std::remove_cv_t<T>;
+        size_t stackSize{};
+        struct Node{
+            valueType value;
+            Node* previous;
+        };
+        Node *topNode{nullptr};
+    public:
+        constexpr explicit Stack(){}
+        constexpr size_t size()const noexcept{
+            return stackSize;
+        }
+        constexpr valueType top()const{
+            if(topNode==nullptr){
+                throw std::runtime_error("the top of the struct stack is nullptr");
+            }
+            return topNode->value;
+        }
+        constexpr bool empty()const noexcept{
+            return topNode == nullptr;
+        }
+        constexpr Stack& push(valueType const& val)noexcept{
+            Node* newNode = new Node{};
+            newNode->value = val;
+            stackSize++;
+            if(topNode==nullptr){
+                topNode = newNode;
+            }else{
+                newNode->previous = topNode;
+                topNode = newNode;
+            }
+            return *this;
+        }
+        constexpr Stack& pop(){
+            if(topNode==nullptr){
+                throw std::runtime_error("the top of the stack is nullptr");
+            }
+            stackSize--;
+            Node* oldNode{topNode};
+            topNode=topNode->previous;
+            delete oldNode;
+            return *this;
+        }
+        ~Stack(){
+            while (topNode!=nullptr) {
+                pop();
+            }
+        }
+    };
+}
\ No newline at end of file
diff --git a/src/12/c6/c6_bst.cpp b/src/12/c6/c6_bst.cpp
new file mode 100644
index 0000000..f0638ee
--- /dev/null
+++ b/src/12/c6/c6_bst.cpp
@@ -0,0 +1,33 @@
+#include "BinarySearchTree.hpp"
+#include "Stack.hpp"
+#include <iostream>
+
+int main(){
+    zt::Stack<int> stk;
+    std::cout<<stk.empty()<<'\n';
+    stk.push(1);
+    stk.push(2);
+    std::cout<<stk.top()<<" "<<stk.size()<<'\n';
+    stk.pop();
+    std::cout<<stk.size()<<'\n';
+    stk.push(10).push(100);
+    std::cout<<std::boolalpha<<stk.size()<<" "<<stk.empty()<<'\n';
+    // try {
+    //     std::cout<<stk.pop().pop().pop().size()<<'\n';
+    // } catch (...) {
+    
+    // }
+    zt::BinarySearchTree<int> bst;
+    bst.insert(9);
+    std::cout<<bst.findMin()<<'\n'<<bst.toString()<<'\n';
+    bst.insert(3);
+    std::cout<<bst.findMin()<<'\n'<<bst.toString()<<'\n';
+    bst.insert(7);
+    std::cout<<bst.findMin()<<'\n'<<bst.toString()<<'\n';
+    bst.insert(1);
+    std::cout<<bst.findMin()<<'\n'<<bst.toString()<<'\n';
+    bst.insert(12);
+    
+    
+    std::cout<<bst.findMin()<<'\n'<<bst.toString()<<'\n';
+}
\ No newline at end of file
diff --git a/vgcore.9671 b/vgcore.9671
new file mode 100644
index 0000000..c7a9dc5
Binary files /dev/null and b/vgcore.9671 differ