2015 | OriginalPaper | Chapter
Simultaneous Time-Space Upper Bounds for Red-Blue Path Problem in Planar DAGs
Authors : Diptarka Chakraborty, Raghunath Tewari
Published in: WALCOM: Algorithms and Computation
Publisher: Springer International Publishing
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In this paper, we consider the
RedBluePath
problem, which states that given a graph
G
whose edges are colored either red or blue and two fixed vertices
s
and
t
in
G
, is there a path from
s
to
t
in
G
that alternates between red and blue edges. The
RedBluePath
problem in planar DAGs is
NL
-complete. We exhibit a polynomial time and
$O(n^{\frac{1}{2}+\epsilon})$
space algorithm (for any
ε
> 0) for the
RedBluePath
problem in planar DAG. We also consider a natural relaxation of
RedBluePath
problem, denoted as
EvenPath
problem. The
EvenPath
problem in DAGs is known to be
NL
-complete. We provide a polynomial time and
$O(n^{\frac{1}{2}+\epsilon})$
space (for any
ε
> 0) bound for
EvenPath
problem in planar DAGs.