fixing inorder traversal

tree/traversal/inorder.py

@@ -1,15 +1,34 @@
+class Node:
+
+    def __init__(self, val, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
 
 
 def inorder(root):
     res = []
     if not root:
         return res
     stack = []
-    while root and stack:
+    while root or stack:
         while root:
             stack.append(root)
             root = root.left
         root = stack.pop()
-        res.add(root.val)
+        res.append(root.val)
         root = root.right
     return res
+
+if __name__ == '__main__':
+    n1 = Node(100)
+    n2 = Node(50)
+    n3 = Node(150)
+    n4 = Node(25)
+    n5 = Node(75)
+    n6 = Node(125)
+    n7 = Node(175)
+    n1.left, n1.right = n2, n3
+    n2.left, n2.right = n4, n5
+    n3.left, n3.right = n6, n7
+    print(inorder(n1))