UGC NET CSE | June 2007 | Part 2 | Question: 5

Question

Which of the following language is regular:

• A. $L=${${a^{n}b^{n}|n\geq 1}$}
• B. $L=${${a^{n}b^{m}c^{n}d^{m}|n,m\geq 1}$}
• C. $L=${${a^{n}b^{m}|n,m\geq 1}$}
• D. $L=${${a^{n}b^{m}c^{n}|n,m\geq 1}$}

Answer 1

option C is the answer.

It is the set of strings in which one or more a's is followed by one or more b's.

Finite automata for the above language is 

where D is dead state, A is the start state,C is final state.

The language is accepted by finite automata.Hence it is regular