English

A tour problem on a toroidal board

Combinatorics 2019-08-30 v2

Abstract

In this paper we study a tour problem that we came cross while studying biembeddings and Heffter arrays, see [D.S. Archdeacon, Heffter arrays and biembedding graphs on surfaces, Electron. J. Combin. 22 (2015) #P1.74]. Let AA be an n×mn\times m toroidal array consisting of filled cells and empty cells. Assume that an orientation R=(r1,,rn)R=(r_1,\dots,r_n) of each row and C=(c1,,cm)C=(c_1,\dots,c_m) of each column of AA is fixed. Given an initial filled cell (i1,j1)(i_1,j_1) consider the list LR,C=((i1,j1),(i2,j2),,(ik,jk), L_{R,C}=((i_1,j_1),(i_2,j_2),\ldots,(i_k,j_k), (ik+1,jk+1),)(i_{k+1},j_{k+1}),\ldots) where jk+1j_{k+1} is the column index of the filled cell (ik,jk+1)(i_k,j_{k+1}) of the row RikR_{i_k} next to (ik,jk)(i_k,j_k) in the orientation rikr_{i_k}, and where ik+1i_{k+1} is the row index of the filled cell of the column Cjk+1C_{j_{k+1}} next to (ik,jk+1)(i_k,j_{k+1}) in the orientation cjk+1c_{j_{k+1}}. We propose the following "Crazy Knight's Tour Problem": Do there exist RR and CC such that the list LR,CL_{R,C} covers all the filled cells of AA? Here we provide a complete solution for the case with no empty cells and we obtain partial results for square arrays where the filled cells follow some specific regular patterns.

Cite

@article{arxiv.1902.05491,
  title  = {A tour problem on a toroidal board},
  author = {Simone Costa and Marco Dalai and Anita Pasotti},
  journal= {arXiv preprint arXiv:1902.05491},
  year   = {2019}
}
R2 v1 2026-06-23T07:41:16.112Z