It is easy to deduce from Ramsey's Theorem that, given positive integers a1, a2, . . . , am and a finite colouring of the set N of positive integers, there exists an injectiv...
We study the problem of minimal triangulation of graphs. One of the first algorithms to solve this problem was Lex M, which was presented in 1976. A new algorithm, and a simplific...
For an integer n 3, a rank-n matroid is called an n-spike if it consists of n three-point lines through a common point such that, for all k {1, 2, . . . , n - 1}, the union of e...
We give an algorithmic characterisation of finite cop-win digraphs. The case of k > 1 cops and k l 1 robbers is then reduced to the one cop case. Similar characterisations are ...
A graph is called biclaw-free if it has no biclaw as an induced subgraph. In this note, we prove that if G is a connected bipartite biclaw-free graph with (G) 5, then G is collap...