نتایج جستجو برای: surface characterization

تعداد نتایج: 986985  

Journal: :Electr. J. Comb. 2011
Zoltán Lóránt Nagy

In this paper we propose a multipartite version of the classical Turán problem of determining the minimum number of edges needed for an arbitrary graph to contain a given subgraph. As it turns out, here the non-trivial problem is the determination of the minimal edge density between two classes that implies the existence of a given subgraph. We determine the critical edge density for trees and ...

Journal: :Inf. Process. Lett. 1996
Leizhen Cai

This paper is concerned with the fixed-parameter tractability of the problem of deciding whether a graph can be made into a graph with a specified hereditary property by deleting at most i vertices, at most j edges, and adding at most k edges, where i, j, k are fixed integers. It is shown that this problem is fixed-parameter tractable whenever the hereditary property can be characterized by a f...

Journal: :SIAM J. Discrete Math. 2016
Nathan Lindzey Ross M. McConnell

Tucker characterized the minimal forbidden submatrices of binary matrices that do not have the consecutive-ones property. We give a linear-time algorithm to find such a minimal one in any binary matrix that does not have the consecutive-ones property. Lekkerkerker and Boland characterized the minimal forbidden induced subgraphs for the class of interval graphs. We give a linear-time algorithm t...

Journal: :Australasian J. Combinatorics 2011
J. Richard Lundgren Breeann Flesch

Interval p-graphs were introduced by Brown et al. in 2002 as a generalization of interval bigraphs [D.E. Brown, S.C. Flink and J.R. Lundgren, Congr. Numer. 157 (2002), 79–93]. Little work has been done towards characterizing them. For interval bigraphs the only known forbidden subgraph characterization is for trees. As it appears to be quite difficult to find a forbidden subgraph characterizati...

Journal: :Journal of Graph Theory 2006
Konstantin A. Rybnikov Thomas Zaslavsky

We examine two criteria for balance of a gain graph, one based on binary cycles and one on circles. The graphs for which each criterion is valid depend on the set of allowed gain groups. The binary cycle test is invalid, except for forests, if any possible gain group has an element of odd order. Assuming all groups are allowed, or all abelian groups, or merely the cyclic group of order 3, we ch...

Journal: :Annals OR 2008
Meltem Öztürk

Semiorders may form the simplest class of ordered sets with a not necessarily transitive indifference relation. Their generalization has given birth to many other classes of ordered sets, each of them characterized by an interval representation, by the properties of its relations or by forbidden configurations. In this paper, we are interested in preference structures having an interval represe...

Journal: :Discrete Mathematics & Theoretical Computer Science 2013
Flavia Bonomo Guillermo Durán Luciano N. Grippo Martín Darío Safe

A graph is probe (unit) interval if its vertices can be partitioned into two sets: a set of probe vertices and a set of nonprobe vertices, so that the set of nonprobe vertices is a stable set and it is possible to obtain a (unit) interval graph by adding edges with both endpoints in the set of nonprobe vertices. Probe (unit) interval graphs form a superclass of (unit) interval graphs. Probe int...

Journal: :CoRR 2013
Nathan Lindzey Ross M. McConnell

Lekkerkerker and Boland characterized the minimal forbidden induced subgraphs for the class of interval graphs. We give a lineartime algorithm to find one in any graph that is not an interval graph. Tucker characterized the minimal forbidden submatrices of matrices that do not have the consecutive-ones property. We give a linear-time algorithm to find one in any matrix that does not have the co...

2013
Nathan Lindzey Ross M. McConnell

Lekkerkerker and Boland characterized the minimal forbidden induced subgraphs for the class of interval graphs. We give a lineartime algorithm to find one in any graph that is not an interval graph. Tucker characterized the minimal forbidden submatrices of matrices that do not have the consecutive-ones property. We give a linear-time algorithm to find one in any matrix that does not have the co...

Journal: :Discrete Mathematics 1999
Peter C. Fishburn William T. Trotter

A poset P = (X, 4 ) is a split semiorder if there are maps a , f : X --* • with a(x)<~f(x)<~a(x) + 1 for every x E X such that x -< y if and only if f ( x ) < a ( y ) and a(x) + 1 < f ( y ) . A split interval order is defined similarly with a(x)+ 1 replaced by b(x), a(x)<~ f(x)<~ b(x), such that x -< y if and only if f ( x ) < a ( y ) and b(x) < f ( y ) . We investigate these generalizations of...

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