Converting Two-Way Nondeterministic Unary Automata into Simpler Automata
نویسندگان
چکیده
We show that, on inputs of length exceeding 5n, any n-state unary two-way nondeterministic 4nite automaton (2nfa) can be simulated by a (2n+2)-state quasi-sweeping 2nfa. Such a result, besides providing a “normal form” for 2nfa’s, enables us to get a subexponential simulation of unary 2nfa’s by two-way deterministic 4nite automata (2dfa’s). In fact, we prove that any n-state unary 2nfa can be simulated by a sweeping 2dfa with O(n log2(n+1)+3 ) states. c © 2002 Elsevier Science B.V. All rights reserved.
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