The method of forced enumeration for nondeterministic automata
Acta Informatica
Nondeterministic space is closed under complementation
SIAM Journal on Computing
A note on the reduction of two-way automata to one-way atuomata
Information Processing Letters
Tally versions of the Savitch and Immerman-Szelepcse´nyi theorems for sublogarithmic space
SIAM Journal on Computing
Exact lower time bounds for computing Boolean functions on CREW PRAMs
Journal of Computer and System Sciences
Two-way automata simulations and unary languages
Journal of Automata, Languages and Combinatorics
Quantum automata and quantum grammars
Theoretical Computer Science
On the power of Las Vegas II: two-way finite automata
Theoretical Computer Science
On the power of Las Vegas for one-way communication complexity, OBDDs, and finite automata
Information and Computation
Introduction To Automata Theory, Languages, And Computation
Introduction To Automata Theory, Languages, And Computation
Converting two-way nondeterministic unary automata into simpler automata
Theoretical Computer Science - Mathematical foundations of computer science
On the power of quantum finite state automata
FOCS '97 Proceedings of the 38th Annual Symposium on Foundations of Computer Science
Nondeterminism and the size of two way finite automata
STOC '78 Proceedings of the tenth annual ACM symposium on Theory of computing
Complementing unary nondeterministic automata
Theoretical Computer Science - Descriptional complexity of formal systems
On the State Complexity of Operations on Two-Way Finite Automata
DLT '08 Proceedings of the 12th international conference on Developments in Language Theory
On the Size Complexity of Rotating and Sweeping Automata
DLT '08 Proceedings of the 12th international conference on Developments in Language Theory
Unambiguous finite automata over a unary alphabet
MFCS'10 Proceedings of the 35th international conference on Mathematical foundations of computer science
Descriptional complexity of unambiguous nested word automata
LATA'11 Proceedings of the 5th international conference on Language and automata theory and applications
State complexity of operations on two-way deterministic finite automata over a unary alphabet
DCFS'11 Proceedings of the 13th international conference on Descriptional complexity of formal systems
Size complexity of rotating and sweeping automata
Journal of Computer and System Sciences
Unambiguous finite automata over a unary alphabet
Information and Computation
Two-Way automata making choices only at the endmarkers
LATA'12 Proceedings of the 6th international conference on Language and Automata Theory and Applications
On multi-head automata with restricted nondeterminism
Information Processing Letters
State complexity of operations on two-way finite automata over a unary alphabet
Theoretical Computer Science
State Complexity of Union and Intersection for Two-way Nondeterministic Finite Automata
Fundamenta Informaticae - Theory that Counts: To Oscar Ibarra on His 70th Birthday
DCFS'12 Proceedings of the 14th international conference on Descriptional Complexity of Formal Systems
Reversal hierarchies for small 2DFAs
MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
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We study the relationship between the sizes of two-way finite automata accepting a language and its complement. In the deterministic case, for a given automaton (2dfa) with n states, we build an automaton accepting the complement with at most 4n states, independently of the size of the input alphabet. Actually, we show a stronger result, by presenting an equivalent 4n-state 2dfa that always halts. For the nondeterministic case, using a variant of inductive counting, we show that the complement of a unary language, accepted by an n-state two-way automaton (2nfa), can be accepted by an O(n^8)-state 2nfa. Here we also make 2nfa's halting. This allows the simulation of unary 2nfa's by probabilistic Las Vegas two-way automata with O(n^8) states.