Take the top plate first
Picture
Put a blue plate down. Put a pink plate on top. The pink one is the easiest to take next. A stack follows this last-in, first-out order.
Predict
Blue goes in first, then pink. Which plate comes out first?
Let's look
Pink, the last one added.
A little Python, if you want it
plates = []
plates.append("blue")
plates.append("pink")
assert plates.pop() == "pink"
assert plates == ["blue"]append adds to the end. pop() takes from that same end. Paused function calls also form a stack: finish the newest unfinished call, then return to its caller.
Change one rule
We want the oldest item first. Would this stack rule do that?
Let's try it
No. We need the queue rule next.
Connect
Compare a queue. Keep the stack picture for recursion and depth-first search.