pushdown automata

Consider the following languages : $$$\eqalign{ & {L_1} = \left\{ {{a^n}{b^m}{c^{n + m}}:m,n \ge 1} \right\} \cr & {L_2} = \left\{ {{a^n}{b^n}{c^{2n}}:n \ge 1} \right\} \cr} $$$ Wh...

Which of the following are decidable? $$1.$$ Whether the intersection of two regular languages is infinite $$2.$$ Whether a given context-free language is regular $$3.$$ Whether tw...

Let $${N_f}$$ and $${N_p}$$ denote the classes of languages accepted by non-deterministic finite automata and non-deterministic push-down automata, respectively. Let $${D_f}$$ and...