2005 | OriginalPaper | Buchkapitel
Characterization and Recognition of Generalized Clique-Helly Graphs
verfasst von : Mitre Costa Dourado, Fábio Protti, Jayme Luiz Szwarcfiter
Erschienen in: Graph-Theoretic Concepts in Computer Science
Verlag: Springer Berlin Heidelberg
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Let
p
≥ 1 and
q
≥ 0 be integers. A family of sets
${\mathcal F}$
is
(p
,q
)-intersecting
when every subfamily
${\mathcal F}' \subseteq {\mathcal F}$
formed by
p
or less members has total intersection of cardinality at least
q
. A family of sets
${\mathcal F}$
is
(p
,q
)-Helly
when every (
p
,
q
)-intersecting subfamily
${\mathcal F}' \subseteq {\mathcal F}$
has total intersection of cardinality at least
q
. A graph
G
is a
(p
,q
)-clique-Helly graph
when its family of (maximal) cliques is (
p
,
q
)-Helly. According to this terminology, the usual Helly property and the clique-Helly graphs correspond to the case
p
=2,
q
=1. In this work we present a characterization for (
p
,
q
)-clique-Helly graphs. For fixed
p
,
q
, this characterization leads to a polynomial-time recognition algorithm. When
p
or
q
is not fixed, it is shown that the recognition of (
p
,
q
)-clique-Helly graphs is NP-hard.