add solution: invert-binary-tree

Author: dusunax

invert-binary-tree/dusunax.py

@@ -0,0 +1,27 @@
+'''
+# 226. Invert Binary Tree
+
+switch left and right child of each node
+
+## TC: O(N)
+
+visit each node once
+
+## SC: O(h)
+
+h is height of tree
+
+- best case: O(logN), balanced tree
+- worst case: O(N), skewed tree
+'''
+class Solution:
+    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
+        if not root:
+            return None
+
+        root.left, root.right = root.right, root.left
+
+        self.invertTree(root.left)
+        self.invertTree(root.right)
+
+        return root