1.Please remove all the unused libs for every files

2.add a file header for all the files

codes/csharp/chapter_tree/avl_tree.cs

@@ -1,6 +1,11 @@
-using hello_algo.include;
+/**
+ * File: avl_tree.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
-using System.Collections.Generic;
 
 namespace hello_algo.chapter_tree
 {
@@ -69,7 +74,7 @@ namespace hello_algo.chapter_tree
         }
 
         /* 执行旋转操作，使该子树重新恢复平衡 */
-        private TreeNode? rotate(TreeNode? node)
+        TreeNode? rotate(TreeNode? node)
         {
             if (node == null)
                 return node;

codes/csharp/chapter_tree/binary_search_tree.cs

@@ -1,7 +1,11 @@
-using hello_algo.include;
-using NUnit.Framework;
-using System.Collections.Generic;
+/**
+ * File: binary_search_tree.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
 
+using hello_algo.include;
+using NUnit.Framework;
 
 namespace hello_algo.chapter_tree
 {
@@ -31,11 +35,7 @@ namespace hello_algo.chapter_tree
             return cur;
         }
 
-        /// <summary>
-        /// 插入结点
-        /// </summary>
-        /// <param name="num"></param>
-        /// <returns></returns>
+        /* 插入结点 */
         TreeNode? insert(int num)
         {
             // 若树为空，直接提前返回

codes/csharp/chapter_tree/binary_tree.cs

@@ -1,7 +1,11 @@
+/**
+ * File: binary_tree.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
 using hello_algo.include;
 using NUnit.Framework;
-using System.Collections.Generic;
-
 
 namespace hello_algo.chapter_tree
 {

codes/csharp/chapter_tree/binary_tree_bfs.cs

@@ -1,4 +1,10 @@
-using hello_algo.include;
+/**
+ * File: binary_tree_bfs.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+using hello_algo.include;
 using NUnit.Framework;
 
 namespace hello_algo.chapter_tree