An improved approximation algorithm for vertex cover with hard capacities

Rajiv Gandhi, Eran Halperin, Samir Khuller, Guy Kortsarz, Aravind Srinivasan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


We study the capacitated vertex cover problem, a generalization of the well-known vertex-cover problem. Given a graph G=(V,E), the goal is to cover all the edges by picking a minimum cover using the vertices. When we pick a vertex, we can cover up to a pre-specified number of edges incident on this vertex (its capacity). The problem is clearly NP-hard as it generalizes the well-known vertex-cover problem. Previously, approximation algorithms with an approximation factor of 2 were developed with the assumption that an arbitrary number of copies of a vertex may be chosen in the cover. If we are allowed to pick at most a fixed number of copies of each vertex, the approximation algorithm becomes much more complex. Chuzhoy and Naor (FOCS, 2002) have shown that the weighted version of this problem is at least as hard as set cover; in addition, they developed a 3-approximation algorithm for the unweighted version. We give a 2-approximation algorithm for the unweighted version, improving the Chuzhoy-Naor bound of three and matching (up to lower-order terms) the best approximation ratio known for the vertex-cover problem.

Original languageEnglish (US)
Pages (from-to)16-33
Number of pages18
JournalJournal of Computer and System Sciences
Issue number1
StatePublished - Feb 2006


  • Approximation algorithms
  • Capacitated covering
  • Linear programming
  • Randomized rounding
  • Set cover
  • Vertex cover

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science
  • Applied Mathematics
  • Computer Networks and Communications
  • Computational Theory and Mathematics


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