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Author: hogan-tech

0145-binary-tree-postorder-traversal/0145-binary-tree-postorder-traversal.py

@@ -0,0 +1,24 @@
+# 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
+
+# time complexity: O(n)
+# space complexity: O(n)
+class Solution:
+    def postorderTraversal(self, root: Optional[TreeNode]) -> List[int]:
+        result = []
+        def traverse(node):
+            if node is None:
+                return
+            if node.left:
+                traverse(node.left)
+            if node.right:
+                traverse(node.right)
+            result.append(node.val)
+            return 
+        traverse(root)
+        return result
+