Rename the common modules.

codes/csharp/utils/TreeNode.cs

@@ -0,0 +1,73 @@
+/**
+ * File: TreeNode.cs
+ * Created Time: 2022-12-23
+ * Author: haptear (haptear@hotmail.com)
+ */
+
+namespace hello_algo.utils;
+
+/* 二叉树节点类 */
+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<int?> arr) {
+        if (arr.Count == 0 || arr[0] == null)
+            return null;
+
+        TreeNode root = new TreeNode(arr[0]!.Value);
+        Queue<TreeNode> queue = new Queue<TreeNode>();
+        queue.Enqueue(root);
+        int i = 0;
+        while (queue.Count != 0) {
+            TreeNode node = queue.Dequeue();
+            if (++i >= arr.Count) break;
+            if (arr[i] != null) {
+                node.left = new TreeNode((int)arr[i]);
+                queue.Enqueue(node.left);
+            }
+            if (++i >= arr.Count) break;
+            if (arr[i] != null) {
+                node.right = new TreeNode((int)arr[i]);
+                queue.Enqueue(node.right);
+            }
+        }
+        return root;
+    }
+
+    /* Serialize a binary tree to a list */
+    public static List<int?> TreeToList(TreeNode root) {
+        List<int?> list = new();
+        if (root == null) return list;
+        Queue<TreeNode?> queue = new();
+        while (queue.Count != 0) {
+            TreeNode? node = queue.Dequeue();
+            if (node != null) {
+                list.Add(node.val);
+                queue.Enqueue(node.left);
+                queue.Enqueue(node.right);
+            } else {
+                list.Add(null);
+            }
+        }
+        return list;
+    }
+
+    /* Get a tree node with specific value in a binary tree */
+    public static TreeNode? GetTreeNode(TreeNode? root, int val) {
+        if (root == null)
+            return null;
+        if (root.val == val)
+            return root;
+        TreeNode? left = GetTreeNode(root.left, val);
+        TreeNode? right = GetTreeNode(root.right, val);
+        return left ?? right;
+    }
+}