A digraph is upward planar if it has a planar drawing such that all the edges are monotone with respect to the vertical direction. Testing upward planarity and constructing upward ...
Paola Bertolazzi, Giuseppe Di Battista, Carlo Mann...
We show that every NP problem is polynomially equivalent to a simple combinatorial problem: the membership problem for a special class of digraphs. These classes are defined by me...
In Formal Concept Analysis, it is a very important but quite difficult task to draw line diagrams of concept lattices automatically. In particular, we want every planar lattice to ...
Let H be a fixed directed graph on h vertices, let G be a directed graph on n vertices and suppose that at least n2 edges have to be deleted from it to make it H-free. We show tha...
Abstract—In any formal theory, a proof is a sequence of well formed formulas (wff). Here, we consider the digraph whose nodes are proofs and the edges are pairs of proofs such t...