Update bt_inorder.py

trees/bt_inorder.py

@@ -2,6 +2,7 @@
 # -*- coding: utf-8 -*-
 # author: bt3gl
 
+
 def inorder(root) -> list:
         
   if root is None:
@@ -9,3 +10,22 @@ def inorder(root) -> list:
     
   return inorder(root.left) + [root.val] + inorder(root.right)
         
+
+def inorder_iterative(root) -> list:
+        
+        result = []
+        stack = []
+        node = root
+        
+        while stack or node:
+
+            if node:
+		stack.append(node)
+                node = node.left
+            else: 
+                node = stack.pop()
+                result.append(node.val)
+                node = node.right
+            
+        return result
+