Fooling a two-way automaton or one pushdown store is better than one counter for two way machines (Preliminary Version)

Authors:
Pavol Dûriš;Zvi Galil
Affiliations:
Computer Center, Slovak Academy of Science, 80943 Bratislava, Czechoslovakia;School of Mathematical Sciences, Tel-Aviv University, Tel-Aviv, Israel
Venue:
STOC '81 Proceedings of the thirteenth annual ACM symposium on Theory of computing
Year:
1981

Citing 4
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Abstract

We define a language L and show that is cannot be recognized by any two way deterministic counter machine. It is done by fooling any given such machine; i.e. showing that if it accepts L' @@@@ L, then L'-L @@@@ &fgr;. For this purpose, an argument stronger than the well known crossing sequence argument needs to be introduced. Since L is accepted by a two-way deterministic pushdown automaton, we consequently show that one pushdown stack is more powerful than one counter for deterministic two-way machines.