Tree 3-spanners in 2-sep chordal graphs: Characterization and algorithms

  • Authors:
  • B. S. Panda;Anita Das

  • Affiliations:
  • Computer Science and Application Group, Department of Mathematics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110 016, India;Department of Computer Science and Automation, Indian Institute of Science, Bangalore 560012, India

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2010

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Abstract

A spanning tree T of a graph G is said to be a treet-spanner if the distance between any two vertices in T is at most t times their distance in G. A graph that has a tree t-spanner is called a treet-spanner admissible graph. The problem of deciding whether a graph is tree t-spanner admissible is NP-complete for any fixed t=4 and is linearly solvable for t@?2. The case t=3 still remains open. A chordal graph is called a 2-sep chordal graph if all of its minimal a-b vertex separators for every pair of non-adjacent vertices a and b are of size two. It is known that not all 2-sep chordal graphs admit tree 3-spanners. This paper presents a structural characterization and a linear time recognition algorithm of tree 3-spanner admissible 2-sep chordal graphs. Finally, a linear time algorithm to construct a tree 3-spanner of a tree 3-spanner admissible 2-sep chordal graph is proposed.