arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2008.01164math.CO
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作为函数的受限堆栈

Restricted Stacks as Functions

Katalin Berlow

摘要:

堆栈排序算法多年来一直是广泛研究的主题。在本文中,我们探讨了这种算法的一个广义版本,而不是避免一个单一的减少,堆栈避免了一组$T$的排列。我们用$s_T$表示这个映射。我们对映射$s_T$对于哪些集合$T$是双射的进行分类。这个推论回答了Baril、Cerbai、Khalil和Vajnovszki关于用$s_{\{σ,τ\}}$组成的堆栈排序的问题,称为$(σ,τ)$ -机器。这完全分类为$σ$和$τ$的身份下的原像$(σ,τ)$ -机器是由加泰罗尼亚数字计数。我们还证明了置换在映射$s_T$下的原像数受Catalan数的约束,且其指数有位移。对于大小为1的$T$,当这个界限是尖锐的时,我们准确地分类。我们还探讨了包含两个长度$3$排列的$T$的各种$s_T$的周期点和最大原像数。

英文摘要:

The stack sort algorithm has been the subject of extensive study over the years. In this paper we explore a generalized version of this algorithm where instead of avoiding a single decrease, the stack avoids a set $T$ of permutations. We let $s_T$ denote this map. We classify for which sets $T$ the map $s_T$ is bijective. A corollary to this answers a question of Baril, Cerbai, Khalil, and Vajnovszki about stack sort composed with $s_{\{σ,τ\}}$, known as the $(σ,τ)$-machine. This fully classifies for which $σ$ and $τ$ the preimage of the identity under the $(σ,τ)$-machine is counted by the Catalan numbers. We also prove that the number of preimages of a permutation under the map $s_T$ is bounded by the Catalan numbers, with a shift of indices. For $T$ of size 1, we classify exactly when this bound is sharp. We also explore the periodic points and maximum number of preimages of various $s_T$ for $T$ containing two length $3$ permutations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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