English

A natural bijection for contiguous pattern avoidance in words

Combinatorics 2023-12-04 v2 Discrete Mathematics Formal Languages and Automata Theory

Abstract

Two words pp and qq are avoided by the same number of length-nn words, for all nn, precisely when pp and qq have the same set of border lengths. Previous proofs of this theorem use generating functions but do not provide an explicit bijection. We give a bijective proof for all pairs p,qp, q that have the same set of proper borders, establishing a natural bijection from the set of words avoiding pp to the set of words avoiding qq.

Keywords

Cite

@article{arxiv.2212.08959,
  title  = {A natural bijection for contiguous pattern avoidance in words},
  author = {Julia Carrigan and Isaiah Hollars and Eric Rowland},
  journal= {arXiv preprint arXiv:2212.08959},
  year   = {2023}
}

Comments

This version is our accepted manuscript. The most important changes from the previous version are as follows. The proof of the main theorem is streamlined, the introduction is updated, and section 4 is omitted. (12 pages, 8 figures)

R2 v1 2026-06-28T07:40:31.715Z