Biconnectivity approximations and graph carvings

  • Authors:
  • Samir Khuller;Uzi Vishkin

  • Affiliations:
  • University of Maryland;University of Maryland, & Tel-Aviv University

  • Venue:
  • STOC '92 Proceedings of the twenty-fourth annual ACM symposium on Theory of computing
  • Year:
  • 1992

Quantified Score

Hi-index 0.00

Visualization

Abstract

A spanning tree in a graph is the smallest connected spanning subgraph. Given a graph, how does one find the smallest (i.e., least number of edges) 2-connected spanning subgraph (connectivity refers to both edge and vertex connectivity, if not specified)? Unfortunately, the problem is known to be NP-hard.We consider the problem of finding an approximation to the smallest 2-connected subgraph, by an efficient algorithm. For 2-edge connectivity our algorithm guarantees a solution that is no more than 3/2 times the optimal. For 2-vertex connectivity our algorithm guarantees a solution that is no more than 5/3 times the optimal. The previous best approximation factor is 2 for each of these problems. The new algorithms (and their analyses) depend upon a structure called a carving of a graph, which is of independent interest. We show that approximating the optimal solution to within an additive constant is NP-hard as well.We also consider the case where the graph has edge weights. We show that an approximation factor of 2 is possible in polynomial time for finding a k-edge connected spanning subgraph. This improves an approximation factor of 3 for k=2 due to [FJ81], and extends it for any k (with an increased running time though).