Tree Traversal - Postorder

Tree Traversal - Postorder

@@ -0,0 +1,31 @@
+
+##Iterative Solution##
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def postorderTraversal(self, root: TreeNode) -> List[int]:
+        #left->right->root
+        stack=[(False,root)]
+        res=[]
+        while stack:
+            flag,val=stack.pop()
+            if val:
+                if not flag:
+                    stack.append((True,val))
+                    stack.append((False,val.right))
+                    stack.append((False,val.left))
+                else:
+                    res.append(val.val)
+        return res
+
+
+##Recursive Solution ##
+      if not root:
+            return []
+        else:
+            return self.postorderTraversal(root.left) + self.postorderTraversal(root.right) + [root.val]