add trees

Author: LEUNGUU

src/trees/invert_binary_tree.py

@@ -0,0 +1,22 @@
+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 not root:
+            return None
+
+        tmp = root.left
+        root.left = root.right
+        root.right = tmp
+
+        self.invertTree(root.left)
+        self.invertTree(root.right)
+        return root