Elevator Interview Problem OOP
I see a few things I would do differently.  For one, I would not use a Queue.  At best, it's providing you an order in which floor buttons were pressed.  While the buttons may be pressed in any order, an elevator moves in sequential order be it up or down.

I would keep a simple List&lt;bool&gt; where true denotes a floor to stop at.  Once you stop at a floor, no need to Dequeue.  Instead just set the flag to false.  By keeping it simple, you won't have to jump through hoops if you are going up but someone presses buttons for 10, 5, 2, 9, 7.