Fun Slot Machines are a variant of the classical ones. Pulling a lever, the player generates a sequence of symbols which are placed on the reels. The machine pays when a given pattern appears in the sequence. The variant consists in trying to transform a losing sequence of symbols in another one, in such a way that the winning pattern does not appear in any intermediate step. The choice of the winning pattern can be crucial; there are "good" and "bad" sequences. The game results in a combinatorial problem on transformations of words avoiding a given pattern as a factor. We investigate "good" and "bad" sequences on a k-ary alphabet and the pairs of words that witness that a word is "bad". A main result is an algorithm to decide whether a word is "bad" or not and to provide a pair of witnesses of minimal length when the word is "bad". It runs in O(n) time with a preprocessing of O(n) time and space to construct an enhanced suffix tree of the word.
@InProceedings{anselmo_et_al:LIPIcs.FUN.2022.4, author = {Anselmo, Marcella and Flores, Manuela and Madonia, Maria}, title = {{Fun Slot Machines and Transformations of Words Avoiding Factors}}, booktitle = {11th International Conference on Fun with Algorithms (FUN 2022)}, pages = {4:1--4:15}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-232-7}, ISSN = {1868-8969}, year = {2022}, volume = {226}, editor = {Fraigniaud, Pierre and Uno, Yushi}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FUN.2022.4}, URN = {urn:nbn:de:0030-drops-159743}, doi = {10.4230/LIPIcs.FUN.2022.4}, annote = {Keywords: Isometric words, Words avoiding factors, Index of a word, Overlap, Lee distance} }
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