English

Finding forest-orderings of tournaments is NP-complete

Combinatorics 2026-01-26 v3

Abstract

Given a class of (undirected) graphs C\mathcal{C}, we say that a Feedback Arc Set (FAS for short) FF is a C\mathcal{C}-FAS if the graph induced by the edges of FF (forgetting their orientations) belongs to C\mathcal{C}. We show that deciding if a tournament has a C\mathcal{C}-FAS is NP-complete when C\mathcal{C} is the class of all forests. We are motivated by connections between C\mathcal{C}-FAS and structural parameters of tournaments, such as the dichromatic number, the clique number of tournaments, and the strong Erd\H{o}s-Hajnal property.

Keywords

Cite

@article{arxiv.2402.10782,
  title  = {Finding forest-orderings of tournaments is NP-complete},
  author = {Pierre Aboulker and Guillaume Aubian and Raul Lopes},
  journal= {arXiv preprint arXiv:2402.10782},
  year   = {2026}
}