Queues and Stacks

[aon]

Do we need to know how to implement a Stack with two Queues or a Queue
with two Stacks or any other combo possible?

[Greg]

You should be very familiar with the properties of each of thes data
structures. You should have a good intuition about how to use them.
They should basically be tools in your toolbox.

Sometimes, we'll ask questions asking you to use them where it is a
good, natural, obvious fit. Sometimes we can ask you questions, such
as the ones you pose, that are designed to test your knowledge around
the edges.

In other words, questions of the form, "Given only X can you build a
Y? If so, how?" So, the questions you ask about queues and stacks are
of value -- as are similar questions for any other data structure.