Handbook of theoretical computer science (vol. B)
SIAM Journal on Computing
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
Introduction to Algorithms
Algorithms for Computing Small NFAs
MFCS '02 Proceedings of the 27th International Symposium on Mathematical Foundations of Computer Science
Word problems requiring exponential time(Preliminary Report)
STOC '73 Proceedings of the fifth annual ACM symposium on Theory of computing
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Classic results in the theory of regular languages show that the problem of converting an NFA (nondeterministic finite automaton) into a minimal equivalent NFA is NP-hard, even for NFAs over a unary alphabet. This paper describes work on fast search techniques for finding minimal NFAs. The foundation of our approach is a characterization theorem for NFAs: we prove that a language is recognized by an n-state NFA iff it has what we call an inductive basis of size n. Using this characterization, we develop a fast incremental search for minimal NFAs for unary languages. We study the performance of our search algorithm experimentally, showing that, as compared with exhaustive search, it cuts the search space dramatically.