#145 Iterative Approach

Author: Parth Shah

145_Binary_Tree_Postorder_Traversal_1.py.py

@@ -0,0 +1,31 @@
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+    def postorderTraversal(self, root):
+        """
+        :type root: TreeNode
+        :rtype: List[int]
+        """
+        result = []
+        stack = []
+        node = root
+        visited = set()
+        while node or stack:
+            if node:
+                stack.append(node)
+                node = node.left
+            else:
+                node = stack.pop()
+                if node.right and not(node.right in visited):
+                    stack.append(node)
+                    node = node.right
+                else:
+                    visited.add(node)
+                    result.append(node.val)
+                    node = None
+        return result