UVa 11995: I Can Guess the Data Structure! simplified problem statement: Given a sequence of push/pop operations, state whether the operations are valid for a queue, stack, priority queue, or some combination thereof (including none thereof). This is a straightforward simulation problem as long as you know how to use STL queues, stacks, and priority_queues. If you don’t, this is a good problem to solve in order to learn how to use them!