Elsevier

Information Processing Letters

Volume 81, Issue 4, 28 February 2002, Pages 175-178
Information Processing Letters

Complexity of homomorphisms to direct products of graphs

https://doi.org/10.1016/S0020-0190(01)00225-3Get rights and content

Abstract

For a graph G, OALG asks whether or not an input graph H together with a partial map g:S→G, SV(H), admits a homomorphism f:H→G such that f|S=g. We show that for connected graphs G1, G2, OAL G1×G2 is in P if G1 and G2 are trees and NP-complete otherwise.

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Cited by (2)

  • On the extension of vertex maps to graph homomorphisms

    2006, Discrete Mathematics
    Citation Excerpt :

    Further studies of retracts are given by Erwin Pesch in [21–23]. The more computational aspect of determining when a given graph is a retract is given in [3,9]. In [25] the retract is studied from the more classical graph-contraction point of view.

1

The research of the first author was partially supported by the Közjóért alapı́tvány Foundation of the National Bank of Hungary, and of the second author by the Hungarian National Fundation for Scientific Research, Grant F32325.

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