diff --git a/homework4/BiTree.h b/homework4/BiTree.h
index 2ef41ac..7065f5f 100644
--- a/homework4/BiTree.h
+++ b/homework4/BiTree.h
@@ -17,6 +17,37 @@ public:
     {
     }
 
+    static bool is_empty(BiTree* bt)
+    {
+        if (bt == nullptr)
+        {
+            return true;
+        }
+        return false;
+    }
+
+    static bool is_leaf(BiTree* bt)
+    {
+        if (bt->left == nullptr && bt->right == nullptr)
+        {
+            return true;
+        }
+        return false;
+    }
+
+    static T sum_leaf(BiTree* bt)
+    {
+        if (is_empty(bt))
+        {
+            return 0;
+        }
+        if (is_leaf(bt))
+        {
+            return bt->data;
+        }
+        return sum_leaf(bt->left) + sum_leaf(bt->right);
+    }
+
     static BiTree* createNode(const T& value)
     {
         BiTree* node = new BiTree();
@@ -26,6 +57,25 @@ public:
         return node;
     }
 
+    static void insertNode(BiTree*& bt, T value)
+    {
+        if (bt == nullptr)
+        {
+            bt = createNode(value);
+        }
+        else
+        {
+            if (value < bt->data)
+            {
+                insertNode(bt->left, value);
+            }
+            if (value > bt->data)
+            {
+                insertNode(bt->right, value);
+            }
+        }
+    }
+
     static BiTree* buildFromPreorderString(const std::string& preorder, size_t& index)
     {
         if (index >= preorder.size() || preorder[index] == '#')
@@ -67,7 +117,7 @@ public:
         this->toStringHelper(oss, "", false, false);
         return oss.str();
     }
-    
+
     void destroy()
     {
         if (left)
diff --git a/homework4/test1.cpp b/homework4/test1.cpp
index 0ba525a..0dd56aa 100644
--- a/homework4/test1.cpp
+++ b/homework4/test1.cpp
@@ -1,17 +1,17 @@
 /*
 * 二叉树采用二叉链存储结构存放，结点值为int 类型，设计一个递归算法求二叉树 bt 中所有叶子结点值之和
  */
-#include<iostream>
-#include"BiTree.h"
+#include <iostream>
+#include "BiTree.h"
+
 using namespace std;
 
-
-BiTree* createTreeFromArray(const int* values, int size)
+BiTree<int>* createTreeFromArray(const int* values, int size)
 {
-    BiTree* root = nullptr;
+    BiTree<int>* root = nullptr;
     for (int i = 0; i < size; ++i)
     {
-        BiTree::insertNode(root, values[i]);
+        BiTree<int>::insertNode(root, values[i]);
     }
     return root;
 }
@@ -21,9 +21,22 @@ int main()
     int testValues[] = {7, 3, 10, 1, 5, 9, 12};
     int size = sizeof(testValues) / sizeof(testValues[0]);
 
-    BiTree* root = createTreeFromArray(testValues, size);
+    BiTree<int>* root = createTreeFromArray(testValues, size);
+
+    if (root)
+    {
+        cout << "树结构为:" << endl;
+        cout << root->toString() << endl;
+
+        cout << "叶子节点数据总和: " << BiTree<int>::sum_leaf(root) << endl;
+
+        root->destroy();
+        delete root;
+    }
+    else
+    {
+        cout << "树为空。" << endl;
+    }
 
-    cout << "树结构为" << endl << root->toString() << endl;
-    cout << "叶子节点数据总和: " << BiTree::sum_leaf(root) << endl;
     return 0;
 }