On NFAs where all states are final, initial, or both

Abstract

We examine questions involving nondeterministic finite automata where all states are final, initial, or both initial and final. First, we prove hardness results for the nonuniversality and inequivalence problems for these NFAs. Next, we characterize the languages accepted. Finally, we discuss some state complexity problems involving such automata. © 2009 Elsevier B.V. All rights reserved.