Linear-time Constant-ratio Approximation Algorithm and Tight Bounds for the Contiguity of Cographs

Christophe Crespelle (1) , Philippe Gambette (2)

1 DANTE - Dynamic Networks : Temporal and Structural Capture Approach
2 LIGM - Laboratoire d'Informatique Gaspard-Monge

In this paper we consider a graph parameter called contiguity which aims at encoding a graph by a linear ordering of its vertices. We prove that the contiguity of cographs is unbounded but is always dominated by O(log n), where n is the number of vertices of the graph. And we prove that this bound is tight in the sense that there exists a family of cographs on n vertices whose contiguity is Omega(log n). In addition to these results on the worst-case contiguity of cographs, we design a linear-time constant-ratio approximation algorithm for computing the contiguity of an arbitrary cograph, which constitutes our main result. As a by-product of our proofs, we obtain a min-max theorem, which is worth of interest in itself, stating equality between the rank of a tree and the minimum height of its path partitions.

Domaines: Algorithme et structure de données [cs.DS]

Christophe Crespelle, Philippe Gambette. Linear-time Constant-ratio Approximation Algorithm and Tight Bounds for the Contiguity of Cographs. Seventh International Workshop on Algorithms and Computation, Feb 2013, Kharagpur, India. pp.126-136, ⟨10.1007/978-3-642-36065-7_13⟩. ⟨hal-00755257⟩