I recently started learning about the chomsky hierarchy and I am preparing myself for an upcoming exam. Often there are tasks to specify the smallest classification of a given formal language. How does one safely find the smallest class the language is included in? Which criterias should one look for when doing so?
- $\{a^nb^mc^md^n\mid m,n\geqslant 1\}$
- $\{a^nb^mc^nd^m\mid m, n\geqslant 1\}$
- $\{a^nw\mid w\in\Sigma^*, n\geqslant 0\}$
- $\{(ab)^n(ba)^n\mid n\geqslant 0\}$
