Binary Search Tree

[dormando]

> In this case we would only just want to show User A one time especially 
> since its a list of user activity. We can't store a hash and just 
> push/pop because of race conditions (our first thought). If anyone has 
> any ideas, I'd really appreciate it!
> 

I don't follow :( Could you try explaining what the problem is in more 
detail, and how a binary tree setup would be better than a one time lock?

I don't really see the above example being a problem even if there is a 
race condition.

-Dormando