Approximation algorithms for restricted cycle covers based on cycle decompositions

  • Authors:
  • Bodo Manthey

  • Affiliations:
  • Informatik, Universität des Saarlandes, Saarbrücken, Germany

  • Venue:
  • WG'06 Proceedings of the 32nd international conference on Graph-Theoretic Concepts in Computer Science
  • Year:
  • 2006

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Abstract

A cycle cover of a graph is a set of cycles such that every vertex is part of exactly one cycle. An L-cycle cover is a cycle cover in which the length of every cycle is in the set L⊆ℕ. For most sets L, the problem of computing L-cycle covers of maximum weight is NP-hard and APX-hard. We devise polynomial-time approximation algorithms for L-cycle covers. More precisely, we present a factor 2 approximation algorithm for computing L-cycle covers of maximum weight in undirected graphs and a factor 20/7 approximation algorithm for the same problem in directed graphs. Both algorithms work for arbitrary sets L. To do this, we develop a general decomposition technique for cycle covers. Finally, we show tight lower bounds for the approximation ratios achievable by algorithms based on such decomposition techniques.