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  1. Home > Articles & Issues >
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  3. Complexity of locall ...
Article

Complexity of locally-injective homomorphisms to tournaments

Stefan Bard, Thomas Bellitto, Christopher Duffy ORCID, Gary MacGillivray, Feiran Yang
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Submitted on
October 26, 2017
Accepted on
September 3, 2018
Published on
November 30, 2018
Last modified on
March 31, 2025
Volume 20
vol. 20:2
Graph Theory
DOI
10.23638/DMTCS-20-2-4
License
arXiv.org - Non-exclusive license to distribute
Natural Sciences and Engineering Research Council of Canada
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1198
Views
634
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Complexity of locally-injective homomorphisms to tournaments

Stefan Bard, Thomas Bellitto, Christopher Duffy ORCID, Gary MacGillivray, Feiran Yang
Abstract
For oriented graphs $G$ and $H$, a homomorphism $f: G \rightarrow H$ is locally-injective if, for every $v \in V(G)$, it is injective when restricted to some combination of the in-neighbourhood and out-neighbourhood of $v$. Two of the possible definitions of local-injectivity are examined. In each case it is shown that the associated homomorphism problem is NP-complete when $H$ is a reflexive tournament on three or more vertices with a loop at every vertex, and solvable in polynomial time when $H$ is a reflexive tournament on two or fewer vertices. Comment: 22 pages, 16 figures
Keywords
  • Computer Science - Discrete Mathematics
  • Mathematics - Combinatorics
  • 05C15
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