11,134 research outputs found
A new problem in string searching
We describe a substring search problem that arises in group presentation
simplification processes. We suggest a two-level searching model: skip and
match levels. We give two timestamp algorithms which skip searching parts of
the text where there are no matches at all and prove their correctness. At the
match level, we consider Harrison signature, Karp-Rabin fingerprint, Bloom
filter and automata based matching algorithms and present experimental
performance figures.Comment: To appear in Proceedings Fifth Annual International Symposium on
Algorithms and Computation (ISAAC'94), Lecture Notes in Computer Scienc
Electric routing and concurrent flow cutting
We investigate an oblivious routing scheme, amenable to distributed
computation and resilient to graph changes, based on electrical flow. Our main
technical contribution is a new rounding method which we use to obtain a bound
on the L1->L1 operator norm of the inverse graph Laplacian. We show how this
norm reflects both latency and congestion of electric routing.Comment: 21 pages, 0 figures. To be published in Springer LNCS Book No. 5878,
Proceedings of The 20th International Symposium on Algorithms and Computation
(ISAAC'09
Routing on the Visibility Graph
We consider the problem of routing on a network in the presence of line
segment constraints (i.e., obstacles that edges in our network are not allowed
to cross). Let be a set of points in the plane and let be a set of
non-crossing line segments whose endpoints are in . We present two
deterministic 1-local -memory routing algorithms that are guaranteed to
find a path of at most linear size between any pair of vertices of the
\emph{visibility graph} of with respect to a set of constraints (i.e.,
the algorithms never look beyond the direct neighbours of the current location
and store only a constant amount of additional information). Contrary to {\em
all} existing deterministic local routing algorithms, our routing algorithms do
not route on a plane subgraph of the visibility graph. Additionally, we provide
lower bounds on the routing ratio of any deterministic local routing algorithm
on the visibility graph.Comment: An extended abstract of this paper appeared in the proceedings of the
28th International Symposium on Algorithms and Computation (ISAAC 2017).
Final version appeared in the Journal of Computational Geometr
Split decomposition and graph-labelled trees: characterizations and fully-dynamic algorithms for totally decomposable graphs
In this paper, we revisit the split decomposition of graphs and give new
combinatorial and algorithmic results for the class of totally decomposable
graphs, also known as the distance hereditary graphs, and for two non-trivial
subclasses, namely the cographs and the 3-leaf power graphs. Precisely, we give
strutural and incremental characterizations, leading to optimal fully-dynamic
recognition algorithms for vertex and edge modifications, for each of these
classes. These results rely on a new framework to represent the split
decomposition, namely the graph-labelled trees, which also captures the modular
decomposition of graphs and thereby unify these two decompositions techniques.
The point of the paper is to use bijections between these graph classes and
trees whose nodes are labelled by cliques and stars. Doing so, we are also able
to derive an intersection model for distance hereditary graphs, which answers
an open problem.Comment: extended abstract appeared in ISAAC 2007: Dynamic distance hereditary
graphs using split decompositon. In International Symposium on Algorithms and
Computation - ISAAC. Number 4835 in Lecture Notes, pages 41-51, 200
Fully Retroactive Approximate Range and Nearest Neighbor Searching
We describe fully retroactive dynamic data structures for approximate range
reporting and approximate nearest neighbor reporting. We show how to maintain,
for any positive constant , a set of points in indexed by time
such that we can perform insertions or deletions at any point in the timeline
in amortized time. We support, for any small constant ,
-approximate range reporting queries at any point in the timeline
in time, where is the output size. We also show how to
answer -approximate nearest neighbor queries for any point in the
past or present in time.Comment: 24 pages, 4 figures. To appear at the 22nd International Symposium on
Algorithms and Computation (ISAAC 2011
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