Stack and Queue problems - underrated topic for interviews

I used to skip stack/queue problems thinking they're too easy. Big mistake. Here are non-trivial ones I've seen in actual interviews:

• Next greater element (monotonic stack)
• Largest rectangle in histogram
• Trapping rain water
• Min stack
• Evaluate reverse polish notation
• Daily temperatures
• Valid parentheses (and its harder variants)
• Sliding window maximum (deque)

The monotonic stack pattern alone has come up in 3 of my interviews this year. Don't sleep on stacks!