Frank R. Libsch, Takatoshi Tsujimura
Active Matrix Liquid Crystal Displays Technology and Applications 1997
Paper
Endmarkers can make a difference
Abstract
We show that the nonemptiness problem for two-way automata with only one endmarker over unary alphabets is complete for nondeterministic logarithmic space. This should be contrasted with the corresponding problem for two-way automata with two endmarkers, which is known to be NP-complete. © 1990.