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Regular Expressions and Finite Automata

GATE CSE 2025 Set 1 · Q28

MSQ1 markEasy

Time

A regular language L L is accepted by a non-deterministic finite automaton (NFA) with n n states. Which of the following statement(s) is/are FALSE?

Select all that applyOne or more correct

Pick every correct option

Solution

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Official answer: D) Every DFA that accepts L has > 2n states.

Regular Expressions and Finite Automata

Let an NFA NN have nn states accepting language LL.

  1. Option (A): *"LL may have an accepting NFA with <n< n states."*

    • This is TRUE. If the given nn-state NFA contains redundant or unreachable states, there may exist an equivalent NFA with fewer states.

  2. Option (B): *"LL may have an accepting DFA with <n< n states."*

    • This is TRUE. An NFA with non-minimal states can be equivalent to a minimal DFA having strictly fewer than nn states (e.g., an NFA with redundant states accepting Σ∗\Sigma^*).

  3. Option (C): *"There exists a DFA with ≤2n\le 2^n states that accepts LL."*

    • This is TRUE. By the subset (powerset) construction, every NFA with nn states can be converted into an equivalent DFA with at most 2n2^n states.

  4. Option (D): *"Every DFA that accepts LL has >2n> 2^n states."*

    • This is FALSE. Since the subset construction always yields an equivalent DFA with at most 2n2^n states, it is impossible for all equivalent DFAs to require more than 2n2^n states.

Since the question asks for the statement(s) that is/are FALSE, the correct option is (D).

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This Regular Expressions and Finite Automata previous year question is Q28 of the GATE CSE 2025 Set 1 paper. Find more GATE CSE PYQs on Regular Expressions and Finite Automata in Theory of Computation, or browse all GATE CSE PYQs.

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Regular Expressions and Finite Automata in GATE CSE

Regular Expressions and Finite Automata has 41 GATE CSE PYQs across 24 papers from 2011 to 2026. 2 of them are 1-mark MSQs like this one, and GATE CSE 2025 Set 1 has 2.

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GateAI solution cardGATE CSE 2025 Set 1 · Q28 · MSQ

A regular language L is accepted by a non-deterministic finite automaton (NFA) with n states. Which of the following statement(s) is/are FALSE?

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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.