Update 0102.二叉树的层序遍历.md

problems/0102.二叉树的层序遍历.md

@@ -2664,24 +2664,31 @@ class Solution {
 Python：
 
 ```python 3
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
 class Solution:
     def maxDepth(self, root: TreeNode) -> int:
-        if root == None:
+        if not root:
             return 0
         
-        queue_ = [root]
         depth = 0
-        while queue_:
-            length = len(queue_)
-            for i in range(length):
-                cur = queue_.pop(0)
-                sub.append(cur.val)
-                #子节点入队列
-                if cur.left: queue_.append(cur.left)
-                if cur.right: queue_.append(cur.right)
+        queue = collections.deque([root])
+        
+        while queue:
             depth += 1
+            for _ in range(len(queue)):
+                node = queue.popleft()
+                if node.left:
+                    queue.append(node.left)
+                if node.right:
+                    queue.append(node.right)
         
         return depth
+
 ```
 
 Go：