feat: 226.invert-binary-tree add Python3 implementation (azl397985856#133)

Author: ybian19

problems/226.invert-binary-tree.md

@@ -39,8 +39,11 @@ Google: 90% of our engineers use the software you wrote (Homebrew), but you can
 
 ## 代码
 
-```js
+* 语言支持：JS，Python
+
+Javascript Code:
 
+```js
 /*
  * @lc app=leetcode id=226 lang=javascript
  *
@@ -122,3 +125,28 @@ var invertTree = function(root) {
  return root;
 };
 ```
+
+Python Code:
+
+```python
+# Definition for a binary tree node.
+# class TreeNode:
+# def __init__(self, x):
+# self.val = x
+# self.left = None
+# self.right = None
+
+class Solution:
+ def invertTree(self, root: TreeNode) -> TreeNode:
+ if not root:
+ return None
+ stack = [root]
+ while stack:
+ node = stack.pop(0)
+ node.left, node.right = node.right, node.left
+ if node.left:
+ stack.append(node.left)
+ if node.right:
+ stack.append(node.right)
+ return root
+```