Near-popular matchings in the roommates problem

  • Authors:
  • Chien-Chung Huang;Telikepalli Kavitha

  • Affiliations:
  • Humboldt-Universität zu Berlin, Germany;Tata Institute of Fundamental Research, India

  • Venue:
  • ESA'11 Proceedings of the 19th European conference on Algorithms
  • Year:
  • 2011

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Abstract

Our input is a graph G = (V,E) where each vertex ranks its neighbors in a strict order of preference. The problem is to compute a matching in G that captures the preferences of the vertices in a popular way. Matching M is more popular than matching M′ if the number of vertices that prefer M to M′ is more than those that prefer M′ to M. The unpopularity factor of M measures by what factor any matching can be more popular than M. We show that G always admits a matching whose unpopularity factor is O(log |V |) and such a matching can be computed in linear time. In our problem the optimal matching would be a least unpopularity factor matching - we show that computing such a matching is NP-hard. In fact, for any ε 0, it is NP-hard to compute a matching whose unpopularity factor is at most 4/3 - ε of the optimal.