invert binary tree

Author: always-maap

226.InvertBinaryTree.py

@@ -0,0 +1,42 @@
+"""
+226. Invert Binary Tree
+Easy
+Tree | Depth-First Search | Breadth-First Search | Binary Tree
+---
+Given the root of a binary tree, invert the tree, and return its root.
+
+Example 1:
+Input: root = [4,2,7,1,3,6,9]
+Output: [4,7,2,9,6,3,1]
+
+Example 2:
+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
+"""
+
+from typing import Optional
+
+
+# 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:
+            root.left, root.right = self.invertTree(root.right), self.invertTree(
+                root.left
+            )
+            return root