diff --git a/problems/0104.二叉树的最大深度.md b/problems/0104.二叉树的最大深度.md
index c4d94d4d..c55ddb3f 100644
--- a/problems/0104.二叉树的最大深度.md
+++ b/problems/0104.二叉树的最大深度.md
@@ -467,22 +467,31 @@ class Solution:
 
 迭代法：
 ```python
-import collections
-class solution:
-    def maxdepth(self, root: 'node') -> int:
-        queue = collections.deque()
-        if root:
-            queue.append(root)
-        depth = 0 #记录深度
+"""
+# Definition for a Node.
+class Node:
+    def __init__(self, val=None, children=None):
+        self.val = val
+        self.children = children
+"""
+
+class Solution:
+    def maxDepth(self, root: TreeNode) -> int:
+        if not root:
+            return 0
+        
+        depth = 0
+        queue = collections.deque([root])
+        
         while queue:
-            size = len(queue)
             depth += 1
-            for i in range(size):
+            for _ in range(len(queue)):
                 node = queue.popleft()
-                for j in range(len(node.children)):
-                    if node.children[j]:
-                        queue.append(node.children[j])
+                for child in node.children:
+                    queue.append(child)
+        
         return depth
+
 ```
 
 使用栈来模拟后序遍历依然可以