Rename the common modules.

codes/java/utils/TreeNode.java

@@ -0,0 +1,67 @@
+/**
+ * File: TreeNode.java
+ * Created Time: 2022-11-25
+ * Author: Krahets (krahets@163.com)
+ */
+
+package utils;
+
+import java.util.*;
+
+/* Definition for a binary tree node. */
+public class TreeNode {
+    public int val; // 节点值
+    public int height; // 节点高度
+    public TreeNode left; // 左子节点引用
+    public TreeNode right; // 右子节点引用
+
+    public TreeNode(int x) {
+        val = x;
+    }
+
+    /* Generate a binary tree given an array */
+    public static TreeNode listToTree(List<Integer> list) {
+        int size = list.size();
+        if (size == 0)
+            return null;
+
+        TreeNode root = new TreeNode(list.get(0));
+        Queue<TreeNode> queue = new LinkedList<>() {{ add(root); }};
+        int i = 0;
+        while (!queue.isEmpty()) {
+            TreeNode node = queue.poll();
+            if (++i >= size)
+                break;
+            if (list.get(i) != null) {
+                node.left = new TreeNode(list.get(i));
+                queue.add(node.left);
+            }
+            if (++i >= size)
+                break;
+            if (list.get(i) != null) {
+                node.right = new TreeNode(list.get(i));
+                queue.add(node.right);
+            }
+        }
+        return root;
+    }
+
+    /* Serialize a binary tree to a list */
+    public static List<Integer> treeToList(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        if (root == null)
+            return list;
+        Queue<TreeNode> queue = new LinkedList<>() {{ add(root); }};
+        while (!queue.isEmpty()) {
+            TreeNode node = queue.poll();
+            if (node != null) {
+                list.add(node.val);
+                queue.add(node.left);
+                queue.add(node.right);
+            } else {
+                list.add(null);
+            }
+        }
+        return list;
+    }
+}