Converting Two-Way Nondeterministic Unary Automata into Simpler Automata

Authors:
Viliam Geffert;Carlo Mereghetti;Giovanni Pighizzini
Affiliations:
-;-;-
Venue:
MFCS '01 Proceedings of the 26th International Symposium on Mathematical Foundations of Computer Science
Year:
2001

Citing 6
Cited 0

Finite automata and unary languages

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Nondeterminism and the size of two way finite automata

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Abstract

We show that, on inputs of length exceeding 5n2, any n- state unary 2nfa (two-way nondeterministic finite automaton) can be simulated by a (2n+2)-state quasi sweeping 2nfa. Such a result, besides providing a "normalform" for 2nfa's, enables us to get a subexponential simulation of unary 2nfa's by 2dfa's (two-way deterministic finite automata). In fact, we prove that any n-state unary 2nfa can be simulated by a 2dfa with O(nlog n+4) states.