Hierarchical graphs are an important class of graphs for modelling many real applications in software and information visualization. In this paper, we shall investigate the computational complexity of constructing minimum area grid visibility representations of hierarchically planar graphs. Firstly, we provide a quadratic algorithm that minimizes the drawing area with respect to a xed planar em...

The augmenting chain technique has been applied to solve the maximum stable set problem in the class of line graphs (which coincides with the maximum matching problem) and then has been extended to the class of claw-free graphs. In the present paper, we propose a further generalization of this approach. Specifically, we show how to find an augmenting chain in graphs containing no skew star, i.e...

The maximum independent set problem is NP-complete for graphs in general, but becomes solvable in polynomial time when restricted to graphs in many special classes. The problem is also intractable from a parameterized point of view. However, very little is known about parameterized complexity of the problem in restricted graph classes. In the present paper, we analyse two techniques that have p...

Several applications of methods from non-linear algebra to the stable set problem in graphs are surveyed. The most recent work sketched is joint with A. Schrijver and involves non-linear inequalities. These yield a procedure to generate facets of the stable set polytope. If a class of graphs has the property that all facets of the stable set polytope can be generated this way in a bounded numbe...

Many classes of graphs where the vertex coloring problem is polynomially solvable are known, the most prominent being the class of perfect graphs. However, the list-coloring problem is NP-complete for many subclasses of perfect graphs. In this work we explore the complexity boundary between vertex coloring and list-coloring on such subclasses of perfect graphs, where the former admits polynomia...

Given an undirected graph G = (V,E) and two positive integers k and d, we are interested in finding a set of edges (resp. non-edges) of size at most k to delete (resp. to add) in such a way that the chromatic number (resp. stability number) in the resulting graph will decrease by at least d compared to the original graph. We investigate these two problems in various classes of graphs (split gra...

Consider a probabilistic graph G in which the edges are perfectly reliable, but vertices may fail with some known probabilities. The 2-terminal reliability of G is defined as the probability that one operational path exists between a given source and destination pair vertices of G. This 2-terminal reliability problem is known to be #P-complete for general graphs but solvable in polynomial time ...

We give a linear-time algorithm to compute the cutwidth of threshold graphs, thereby resolving the computational complexity of cutwidth on this graph class. Although our algorithm is simple and intuitive, its correctness proof relies on a series of non-trivial structural results, and turns out to be surprisingly complex. Threshold graphs are a well-studied subclass of interval graphs and of spl...

Let G denote a graph, and KV(G) represent a set of target vertices. Assume that the non-target vertices of G fail independently with given probabilities. The K-terminal reliability of G is defined as the probability that all target vertices in K are connected. Computing K-terminal reliability is #P-complete for general graphs, yet solvable in polynomial time for interval graphs. This work prop...