第二题初步完成

homework4/BiTree.h

@@ -2,7 +2,6 @@
 #define BITREE_H
 #include<sstream>
 
-
 class BiTree
 {
 public:
@@ -10,13 +9,15 @@ public:
     BiTree* left;
     BiTree* right;
 
-
     static bool is_empty(BiTree* bt);
     static bool is_leaf(BiTree* bt);
     static int sum_leaf(BiTree* bt);
     static BiTree* createNode(int data);
     static void insertNode(BiTree*& bt, int value);
+    static BiTree* build_from_preorder_string(const std::string& preorder, size_t& index);
+    void inOrder(std::ostringstream& oss) const;
     std::string toString();
+    void destory();
 };