python 3.x - I am trying zig zag traversal of a binary tree. its not printing 5 of the last branch, can anybody tell me why? -

there no indentation problem in code

    class node:       def __init__(self,key):         self.data=key         self.left=none         self.right=none    def zig_zag(root):     if not root:         return     s=[]     l=1     s.append(root)      while s:         q=[]         if l%2==1:             in reversed(s):                 print(i.data,end=' ')                 if i.left:q.append(i.left)                 if i.right:q.append(i.right)          else:             in s:                 print(i.data,end=' ')                 if i.left:q.append(i.left)                 if i.right:q.append(i.right)         print(q)             s=q         l+=1 root=node(1) root.left=node(2) root.right=node(3) root.left.left=node(7) root.left.right=node(6) root.right.left=node(5) root.right.left=node(4) zig_zag(root) 

the output getting [1,2,3,4,6,7] instead of [1,2,3,4,5,6,7].can explain why not appending 5 last branch of tree

algorithm fine.
have made mistake in "node adding code"
setting root.right.left twice

change

root.right.left=node(5) root.right.left=node(4) 

to

root.right.left=node(5) root.right.right=node(4)