2012 | OriginalPaper | Chapter
Solving the 2-Disjoint Connected Subgraphs Problem Faster Than 2 n
Authors : Marek Cygan, Marcin Pilipczuk, Michał Pilipczuk, Jakub Onufry Wojtaszczyk
Published in: LATIN 2012: Theoretical Informatics
Publisher: Springer Berlin Heidelberg
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The
2-Disjoint Connected Subgraphs
problem, given a graph along with two disjoint sets of terminals
Z
1
,
Z
2
, asks whether it is possible to find disjoint sets
A
1
,
A
2
, such that
Z
1
⊆
A
1
,
Z
2
⊆
A
2
and
A
1
,
A
2
induce connected subgraphs. While the naive algorithm runs in
O
(2
n
n
O
(1)
) time, solutions with complexity of form
O
((2 −
ε
)
n
) have been found only for special graph classes [15, 19]. In this paper we present an
O
(1.933
n
) algorithm for
2-Disjoint Connected Subgraphs
in general case, thus breaking the 2
n
barrier. As a counterpoise of this result we show that if we parameterize the problem by the number of non-terminal vertices, it is hard both to speed up the brute-force approach and to find a polynomial kernel.