Larger stack size

[Gene]

Bigger picture IMO is that most of these types of problems are contrived. They are unlikely to reflect "real life" situations and are laid out to showcase a weakness in an OS or operating approach.

So a 4 level RPN stack works for nearly anything as long as you can store values into registers if needed.

An AOS approach works for nearly everything (having a "real life" problem with more than 8 pending operations would be awful)...

And an EOS approach works for everything (pretty much - I suppose you could run out of ram typing it in).

:-)