Parallel algorithms for Hamiltonian problems on quasi-threshold graphs

  • Authors:
  • Stavros D. Nikolopoulos

  • Affiliations:
  • Department of Computer Science, University of Ioannina, P.O. Box 1186, GR-45110 Ioannina, Greece

  • Venue:
  • Journal of Parallel and Distributed Computing
  • Year:
  • 2004

Quantified Score

Hi-index 0.00

Visualization

Abstract

In this paper we show structural and algorithmic properties on the class of quasi-threshold graphs, or QT-graphs for short, and prove necessary and sufficient conditions for a QT-graph to be Hamiltonian. Based on these properties and conditions, we construct an efficient parallel algorithm for finding a Hamiltonian cycle in a QT-graph; for an input graph on n vertices and m edges, our algorithm takes O(log n) time and requires O(n + m) processors on the CREW PRAM model. In addition, we show that the problem of recognizing whether a QT-graph is a Hamiltonian graph and the problem of computing the Hamiltonian completion number of a nonHamiltonian QT-graph can also be solved in O(log n) time with O(n + m) processors. Our algorithms rely on O(log n)-time parallel algorithms, which we develop here, for constructing tree representations of a QT-graph; we show that a QT- graph G has a unique tree representation, that is, a tree structure which meets the structural properties of G. We also present parallel algorithms for other optimization problems on QT-graphs which run in O(log n) time using a linear number of processors.