Here is my half adder solution. KV, you mentioned a totally divergent track. I think I know what you mean. So that you have lots of "end points" and the track will look like a tree.
Yeah! I hadn't considered doing it until I saw your solution. Impractical for larger circuits, though.
(http://i.imgur.com/AUqLgyn.png)
Truth table for proof. (This is from sandbox mode.)
(http://i.imgur.com/lHoqJCl.png)