invert-bt py3

0226_invert-binary-tree/README.md

@@ -0,0 +1,30 @@
+Given the `root` of a binary tree, invert the tree, and return _its root_.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2021/03/14/invert1-tree.jpg)
+
+    Input: root = [4,2,7,1,3,6,9]
+    Output: [4,7,2,9,6,3,1]
+    
+
+**Example 2:**
+
+![](https://assets.leetcode.com/uploads/2021/03/14/invert2-tree.jpg)
+
+    Input: root = [2,1,3]
+    Output: [2,3,1]
+    
+
+**Example 3:**
+
+    Input: root = []
+    Output: []
+    
+
+**Constraints:**
+
+*   The number of nodes in the tree is in the range `[0, 100]`.
+*   `-100 <= Node.val <= 100`
+
+https://leetcode.com/problems/invert-binary-tree

0226_invert-binary-tree/python3/solution.py

@@ -0,0 +1,16 @@
+# 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 invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        if root is None: return None
+        
+        root.left, root.right = root.right, root.left
+        
+        self.invertTree(root.left)
+        self.invertTree(root.right)
+        
+        return root