Abstract
Given a language L and a number ℓ, an ℓ-cover automaton for L is a DFA M such that its language coincides with L on all words of length at most ℓ. It is known that an equivalent minimal ℓ-cover automaton can be constructed in time \(\mathcal{O}(n \log n)\), where n is the number of states of M. This is achieved by a clever and sophisticated variant of Hopcroft’s algorithm, which computes the ℓ-similarity inside the main algorithm. This contribution presents an alternative simple algorithm with running time \(\mathcal{O}(n \log n)\), in which the computation is split into three phases. First, a compact representation of the gap table is created. Second, this representation is enriched with information about the length of a shortest word leading to the states. These two steps are independent of the parameter ℓ. Third, the ℓ-similarity is extracted by simple comparisons against ℓ. In particular, this approach allows the calculation of all the sizes of minimal ℓ-cover automata (for all valid ℓ) in the same time bound.
This work was done when A. Maletti was visiting Wrocław University thanks to the support of the “Visiting Professors” programme of the Municipality of Wrocław.
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Jeż, A., Maletti, A. (2011). Computing All ℓ-Cover Automata Fast. In: Bouchou-Markhoff, B., Caron, P., Champarnaud, JM., Maurel, D. (eds) Implementation and Application of Automata. CIAA 2011. Lecture Notes in Computer Science, vol 6807. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-22256-6_19
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DOI: https://doi.org/10.1007/978-3-642-22256-6_19
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