I am studying pushdown automata and I am working on a problem that asks to generate a PDA that accepts the following regular languages:

Intersection of L1 and L2

L1 = L (aaa* bab)
L2 = L (aab* aba)

I can't tell if this is even possible because I don't see any common string that would be in both languages.

If it is not possible how should I formally state so? I am brand new to PDAs.


1 Answer 1


If the intersection is empty then you have to show that some PDA accepts the empty language. That doesn't sound too difficult.

More generally, every NFA is secretly a PDA (showing that every regular language is context-free), and so if you can construct an NFA for your language then you can easily convert it to a PDA.


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