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Discrete Mathematics & Theoretical Computer Science |
Frédérique Bassino ; Julien Clément ; J. Fayolle ; P. Nicodème - Counting occurrences for a finite set of words: an inclusion-exclusion approach
dmtcs:3543 - Discrete Mathematics & Theoretical Computer Science, January 1, 2007, DMTCS Proceedings vol. AH, 2007 Conference on Analysis of Algorithms (AofA 07) - https://doi.org/10.46298/dmtcs.3543
1; Julien Clément 2; J. Fayolle 3; P. Nicodème 4
- 1 Laboratoire d'Informatique Gaspard-Monge
- 2 Equipe AMACC - Laboratoire GREYC - UMR6072
- 3 Laboratoire de Recherche en Informatique
- 4 Laboratoire d'informatique de l'École polytechnique [Palaiseau]
In this paper, we give the multivariate generating function counting texts according to their length and to the number of occurrences of words from a finite set. The application of the inclusion-exclusion principle to word counting due to Goulden and Jackson (1979, 1983) is used to derive the result. Unlike some other techniques which suppose that the set of words is reduced (<i>i..e.</i>, where no two words are factor of one another), the finite set can be chosen arbitrarily. Noonan and Zeilberger (1999) already provided a MAPLE package treating the non-reduced case, without giving an expression of the generating function or a detailed proof. We give a complete proof validating the use of the inclusion-exclusion principle and compare the complexity of the method proposed here with the one using automata for solving the problem.