We show that the adjacency matrix M of the line digraph of a d-regular digraph D on n vertices can be written as M = AB, where the matrix A is the Kronecker product of the all-one...
In the precoloring extension problem we are given a graph with some of the vertices having a preassigned color and it has to be decided whether this coloring can be extended to a ...
: In this paper we consider the edge ranking problem of weighted trees. We prove that a special instance of this problem, namely edge ranking of multitrees is NP-hard already for m...
We give an elementary proof for the Positivity Problem for second order recurrent sequences: it is decidable whether or not a recurrent sequence defined by un = aun-1 + bun-2 has ...