Packing triangles in low degree graphs and indifference graphs

Gordana Manić (1) , Yoshiko Wakabayashi (1)

1 IME - Instituto de Matemática e Estatística

We consider the problems of finding the maximum number of vertex-disjoint triangles (VTP) and edge-disjoint triangles (ETP) in a simple graph. Both problems are NP-hard. The algorithm with the best approximation guarantee known so far for these problems has ratio $3/2 + ɛ$, a result that follows from a more general algorithm for set packing obtained by Hurkens and Schrijver in 1989. We present improvements on the approximation ratio for restricted cases of VTP and ETP that are known to be APX-hard: we give an approximation algorithm for VTP on graphs with maximum degree 4 with ratio slightly less than 1.2, and for ETP on graphs with maximum degree 5 with ratio 4/3. We also present an exact linear-time algorithm for VTP on the class of indifference graphs.

Mots clés: triangle packing; approximation algorithm; polynomial algorithm; low degree graph; indifference graph

Domaines: Mathématique discrète [cs.DM]; Combinatoire [math.CO]

Gordana Manić, Yoshiko Wakabayashi. Packing triangles in low degree graphs and indifference graphs. 2005 European Conference on Combinatorics, Graph Theory and Applications (EuroComb '05), 2005, Berlin, Germany. pp.251-256, ⟨10.46298/dmtcs.3408⟩. ⟨hal-01184365⟩