The Set Connector Problem in Graphs

  • Authors:
  • Takuro Fukunaga;Hiroshi Nagamochi

  • Affiliations:
  • Department of Applied Mathematics and Physics, Graduate School of Informatics, Kyoto University, Japan;Department of Applied Mathematics and Physics, Graduate School of Informatics, Kyoto University, Japan

  • Venue:
  • IPCO '07 Proceedings of the 12th international conference on Integer Programming and Combinatorial Optimization
  • Year:
  • 2007

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Abstract

Given a graph G= (V,E) with an edge cost and families $\mathcal{V}_i\subseteq 2^V$, i= 1,2,...,mof disjoint subsets, an edge subset F茂戮驴 Eis called a set connector if, for each $\mathcal{V}_i$, the graph $(V,F)/\mathcal{V}_i$ obtained from (V,F) by contracting each $X\in \mathcal{V}_i$ into a single vertex xhas a property that every two contracted vertices xand x茂戮驴 are connected in $(V,F)/\mathcal{V}_i$. In this paper, we introduce a problem of finding a minimum cost set connector, which contains several important network design problems such as the Steiner forest problem, the group Steiner tree problem, and the NA-connectivity augmentation problem as its special cases. We derive an approximate integer decomposition property from a fractional packing theorem of set connectors, and present a strongly polynomial 2茂戮驴-approximation algorithm for the set connector problem, where $\alpha=\max_{1 \leq i \leq m}(\sum_{X \in \mathcal{V}_i}|X|)-1$.