Converting nondeterministic two-way automata into small deterministic linear-time machines

Converting Two-Way Nondeterministic Unary Automata into Simpler Automata

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 s...

Converting Nondeterministic Automata and Context-Free Grammars into Parikh Equivalent One-Way and Two-Way Deterministic Automata

We investigate the conversion of one-way nondeterministic finite automata and context-free grammars into Parikh equivalent oneway and two-way deterministic finite automata, from a descriptional complexity point of view. We prove that for each one-way nondeterministic automaton with n states there exist Parikh equivalent one-way and two-way deterministic automata with e √ n·lnn) and p(n) states,...

Converting Nondeterministic Automata and Context-Free Grammars into Parikh Equivalent Deterministic Automata

We investigate the conversion of nondeterministic finite automata and context-free grammars into Parikh equivalent deterministic finite automata, from a descriptional complexity point of view. We prove that for each nondeterministic automaton with n states there exists a Parikh equivalent deterministic automaton with e √ n·lnn) states. Furthermore, this cost is tight. In contrast, if all the st...

Converting Self-verifying Automata into Deterministic Automata

Regularly Extended Two-Way Nondeterministic Tree Automata

We establish that regularly extended two-way nondeterministic tree automata with unranked alphabets have the same expressive power as regularly extended nondeterministic tree automata with unranked alphabets. We obtain this result by establishing regularly extended versions of a congruence on trees and of a congruence on, so called, views. Our motivation for the study of these tree models is th...