Paper 3, Section II, G

Automata and Formal Languages
Part II, 2018

(a) State and prove the pumping lemma for regular languages.

(b) Let DD be a minimal deterministic finite-state automaton whose language L(D)\mathcal{L}(D) is finite. Let ΓD\Gamma_{D} be the transition diagram of DD, and suppose there exists a non-empty closed path γ\gamma in ΓD\Gamma_{D} starting and ending at state pp.

(i) Show that there is no path in ΓD\Gamma_{D} from pp to any accept state of DD.

(ii) Show that there is no path in ΓD\Gamma_{D} from pp to any other state of DD.