The State Complexities of Some Basic Operations on Regular Languages

Abstract We consider the state complexities of some basic operations on regular languages. We show that the number of states that is sufficient and necessary in the worst case for a deterministic finite automaton (DFA) to accept the catenation of an m-state DFA language and an n-state DFA language is exactly m2n − 2n − 1, for m, n ⩾ 1. The result of 2n − 1 + 2n − 2 states is obtained for the star of an n-state DFA language, n1. State complexities for other basic operations and for regular languages over a one-letter alphabet are also studied.