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Article Dans Une Revue Theoretical Computer Science Année : 2022

Gray codes for Fibonacci q-decreasing words


An $n$-length binary word is $q$-decreasing, $q\geq 1$, if every of its length maximal factor of the form $0^a1^b$ satisfies $a=0$ or $q\cdot a > b$.We show constructively that these words are in bijection with binary words having no occurrences of $1^{q+1}$, and thus they are enumerated by the $(q+1)$-generalized Fibonacci numbers. We give some enumerative results and reveal similarities between $q$-decreasing words and binary words having no occurrences of $1^{q+1}$ in terms of frequency of $1$ bit. In the second part of our paper, we provide an efficient exhaustive generating algorithm for $q$-decreasing words in lexicographic order, for any $q\geq 1$, show the existence of 3-Gray codes and explain how a generating algorithm for these Gray codes can be obtained. Moreover, we give the construction of a more restrictive 1-Gray code for $1$-decreasing words, which in particular settles a conjecture stated recently in the context of interconnection networks by E\u{g}ecio\u{g}lu and Ir\v{s}i\v{c}.

Dates et versions

hal-03114503 , version 1 (19-01-2021)



Jean-Luc Baril, Sergey Kirgizov, Vincent Vajnovszki. Gray codes for Fibonacci q-decreasing words. Theoretical Computer Science, 2022, 927, pp.120-132. ⟨10.1016/j.tcs.2022.06.003⟩. ⟨hal-03114503⟩
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