feat: 104.maximum-depth-of-binary-tree add Python3 implementation (az…

…l397985856#79)

problems/104.maximum-depth-of-binary-tree.md

@@ -49,7 +49,7 @@ var maxDepth = function(root) {
 - 树的基本操作- 遍历 - 层次遍历（BFS）
 
 ## 代码
-* 语言支持：JS，C++
+* 语言支持：JS，C++，Python
 
 JavaScript Code:
 ```js
@@ -130,6 +130,23 @@ public:
     }
 };
 ```
+
+Python Code:
+```python
+class Solution:
+    def maxDepth(self, root: TreeNode) -> int:
+        if not root: return 0
+        q, depth = [root, None], 1
+        while q:
+            node = q.pop(0)
+            if node:
+                if node.left: q.append(node.left)
+                if node.right: q.append(node.right)
+            elif q:
+                q.append(None)
+                depth += 1
+        return depth
+```
 ## 相关题目
 - [102.binary-tree-level-order-traversal](./102.binary-tree-level-order-traversal.md)
 - [103.binary-tree-zigzag-level-order-traversal](./103.binary-tree-zigzag-level-order-traversal.md)