From 63e6777d470eefac9a59e65d924d7235149836dc Mon Sep 17 00:00:00 2001
From: CyC2018 <zhengyc101@163.com>
Date: Fri, 30 Oct 2026 20:18:06 +0800
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补充二叉树深度的递归计算规则说明。
---
 notes/55.1 二叉树的深度.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/notes/55.1 二叉树的深度.md b/notes/55.1 二叉树的深度.md
index 3af67c60..d0b2f1f3 100644
--- a/notes/55.1 二叉树的深度.md	
+++ b/notes/55.1 二叉树的深度.md	
@@ -10,6 +10,8 @@
 
 ## 解题思路
 
+树的深度等于左右子树深度的较大值加 1，空树的深度为 0。
+
 ```java
 public int calculateDepth(TreeNode root) {
     return root == null ? 0 : 1 + Math.max(calculateDepth(root.left), calculateDepth(root.right));