We present a fully dynamic algorithm for split graphs that supports the following types of operations: (1) query whether deleting or inserting an edge preserves the split property, (2) query whether inserting a new vertex with a given neighborhood in the current graph preserves the split property, (3) insert or delete an edge or a vertex when the split property is preserved, (4) insert an edge ...

We discuss matrix partition problems for graphs that admit a partition into k independent sets and ` cliques. We show that when k + ` 6 2, any matrix M has finitely many (k, `) minimal obstructions and hence all of these problems are polynomial time solvable. We provide upper bounds for the size of any (k, `) minimal obstruction when k = ` = 1 (split graphs), when k = 2, ` = 0 (bipartite graphs...

A graph is a split graph if its vertices can be partitioned into a clique and a stable set. A graph is a k-split graph if its vertices can be partitioned into k sets, each of which induces a split graph. We show that the strong perfect graph conjecture is true for 2-split graphs and we design a polynomial algorithm to recognize a perfect 2-split graph.

A graph containment problem is to decide whether one graph can be modified into some other graph by using a number of specified graph operations. We consider edge deletions, edge contractions, vertex deletions and vertex dissolutions as possible graph operations permitted. By allowing any combination of these four operations we capture the following ten problems: testing on (induced) minors, (i...

A rainbow path in an edge coloured graph is a path in which no two edges are coloured the same. A rainbow colouring of a connected graph G is a colouring of the edges of G such that every pair of vertices in G is connected by at least one rainbow path. The minimum number of colours required to rainbow colour G is called its rainbow connection number. Between them, Chakraborty et al. [J. Comb. O...

Akers et al. (Proceedings of the International Conference on Parallel Processing, 1987, pp. 393–400) proposed an interconnection topology, the star graph, as an alternative to the popular n-cube. Jwo et al. (Networks 23 (1993) 315–326) studied the alternating group graph An. Cheng et al. (Super connectivity of star graphs, alternating group graphs and split-stars, Ars Combin. 59 (2001) 107–116)...

A problem is said to be GI-complete if it is provably as hard as graph isomorphism; that is, there is a polynomial-time Turing reduction from the graph isomorphism problem. It is known that the GI problem is GI-complete for some special graph classes including regular graphs, bipartite graphs, chordal graphs and split graphs. In this paper, we prove that deciding isomorphism of double split gra...

We introduce I/O-effiient certifying algorithms for bipartite graphs, as well the classes of split, threshold, chain, and trivially perfect graphs. When input graph is a member respective class, algorithm returns certificate that characterizes this class. Otherwise, it forbidden induced subgraph non-membership. On with n vertices m edges, our take $$O( {\textsc {sort}(n + m)} ) $$ I/Os in worst...

Hadwiger’s conjecture states that for every graph G, χ(G) ≤ η(G), where χ(G) is the chromatic number and η(G) is the size of the largest clique minor in G. In this work, we show that to prove Hadwiger’s conjecture in general, it is sufficient to prove Hadwiger’s conjecture for the class of graphs F defined as follows: F is the set of all graphs that can be expressed as the square graph of a spl...

We introduce a special decomposition, the so-called split-minors, of the reduced clique graphs of chordal graphs. Using this notion, we characterize asteroidal sets in chordal graphs and clique trees with minimum number of leaves.