Exploració per autor "Thilikos Touloupas, Dimitrios"
Ara es mostren els items 15-34 de 37
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Derivation of algorithms for cutwidth and related graph layout problems
Bodlaender, Hans; Michael, Fellows; Thilikos Touloupas, Dimitrios (2002-07)
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Accés obertIn this paper, we investigate algorithms for some related graph parameters. Each of these asks for a linear ordering of the vertices of the graph (or can be formulated as such), and there are constructive linear time ... -
Dominating sets and local treewidth
Thilikos Touloupas, Dimitrios; Fomin, Fedor V. (2003-09)
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Accés obertIt is known that the treewidth of a planar graph with a dominating set of size d is O(sqrt{d}) and this fact is used as the basis for several fixed parameter algorithms on planar graphs. An interesting question ... -
Dominating sets in planar graphs: branch-width and exponential speed-up
Fomin, Fedor V.; Thilikos Touloupas, Dimitrios (2002-12)
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Accés obertGraph minors theory, developed by Robertson & Seymour, provides a list of powerful theoretical results and tools. However, the wide spread opinion in Graph Algorithms community about this theory is that it is mainly of ... -
Efficient algorithms for parameterized H-colorings
Díaz Cort, Josep; Serna Iglesias, María José; Thilikos Touloupas, Dimitrios (2005-12)
Report de recerca
Accés obertWe study the fixed parameter tractability of the restrictive $H$-coloring and the restrictive list $H$-coloring problems, introduced in~cite{DST01b}. The parameterizations are defined by fixing the number of pre-images of ... -
Exponential speedup of fixed parameter algorithms on K_{3,3}-minor-free or K_{5}-minor-free graphs
Hajiaghayi, Mohammad Taghi; Demaine, Erik D.; Thilikos Touloupas, Dimitrios (2002-03)
Report de recerca
Accés obertWe present a fixed parameter algorithm that constructively solves the k-dominating set problem on graphs excluding one of the K_{5} or K_3,3 as a minor in time O(3^{6sqrt{34 k}}n^{O(1)}). In fact, we present our ... -
Fast approximation schemes for K_{3,3}-minor-free or K_{5}-minor-free graphs
Hajiaghayi, Mohammad Taghi; Nishimura, Naomi; Ragde, Prabhakar; Thilikos Touloupas, Dimitrios (2002-05)
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Accés obertAs the class of graphs of bounded treewidth is of limited size, we need to solve NP-hard problems for wider classes of graphs than this class. Eppstein introduced a new concept which can be considered as a generalization ... -
Fast fixed-parameter tractable algorithms for (nontrivial) generalizations of vertex cover
Nishimura, Naomi; Ragde, Prabhakar; Thilikos Touloupas, Dimitrios (2001-09)
Report de recerca
Accés obertOur goal in this paper is the development of fast algorithms for recognizing general classes of graphs. We seek algorithms whose complexity can be expressed as a linear function of the graph size plus an exponential function ... -
Finding smallest supertrees under minor containment
Nishimura, Naomi; Prabhakar, Ragde; Thilikos Touloupas, Dimitrios (1999-10)
Report de recerca
Accés obertThe diversity of application areas relying on tree-structured data results in a wide interest in algorithms which determine differences or similarities among trees. One way of measuring the similarity between trees ... -
Fixed-parameter algorithms for the (k,r)-center in planar graphs and map graphs
Demaine, Erik D.; Fomin, Fedor V.; Hajiaghayi, Mohammad Taghi; Thilikos Touloupas, Dimitrios (2003-09)
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Accés obertThe (k,r)-center problem} asks whether an input graph G has atr most k vertices (called centers) such that every vertex of $ is within distance at most r from some center. In this paper we prove that the (k,r)-center ... -
(H,C,K)-colorings: fast, easy, and hard cases
Díaz Cort, Josep; Serna Iglesias, María José; Thilikos Touloupas, Dimitrios (2001-05)
Report de recerca
Accés obertWe define a variant of the H-coloring problem by fixing the number of preimages of a subset C of the vertices of H, thus allowing parameterization. We provide sufficient conditions to guarantee that the problem can be ... -
Monotonicity and inert fugitive search games
Stamatiou, Yannis; Thilikos Touloupas, Dimitrios (1999-10)
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Accés obertIn general, graph search can be described in terms of a sequence of searchers' moves on a graph, able to capture a fugitive resorting on its vertices/edges. Several variations of graph search have been introduced, ... -
New upper bounds on the decomposability of planar graphs and fixed parameter algorithms
Fomin, Fedor V.; Thilikos Touloupas, Dimitrios (2002-08)
Report de recerca
Accés obertIt is known that a planar graph on n vertices has branch-width/tree-width bounded by alphasqrt{n}. In many algorithmic applications it is useful to have a small bound on the constant alpha. We give a ... -
On graph powers for leaf-labeled trees
Nishimura, Naomi; Prabhakar, Ragde; Thilikos Touloupas, Dimitrios (2000-07)
Report de recerca
Accés obertWe extend the well-studied concept of a graph power to that of a k-leaf power G of a tree T: G is formed by creating a node for each leaf in the tree and an edge between a pair of nodes if and only if the associated ... -
On the existence of Nash equilibria in strategic search games
Álvarez Faura, M. del Carme; Duch Brown, Amalia; Serna Iglesias, María José; Thilikos Touloupas, Dimitrios (2011)
Text en actes de congrés
Accés obertWe consider a general multi-agent framework in which a set of n agents are roaming a network where m valuable and sharable goods (resources, services, information ....) are hidden in m different vertices of the network. ... -
On the monotonicity of games generated by symmetric submodular functions
Fomin, Fedor V.; Thilikos Touloupas, Dimitrios (2001-02)
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Accés obertSubmodular functions have appeared to be a key tool for proving the monotonicity of several graph searching games. In this paper we provide a general game theoretic framework able to unify old and new monotonicity ... -
Outerplanar obstructions for the vertex feedback set
Rué Perna, Juan José; Thilikos Touloupas, Dimitrios; Stavropoulos, Konstantinos (2012-07-02)
Article
Accés obertFor k = 1, let Fk be the class of graphs that contains k vertices meeting all its cycles. The minor-obstruction set for Fk is the set obs(Fk) containing all minor-minimal graphs that do not belong to Fk. We denote by Yk ... -
Problems and conjectures on parameterized H-coloring
Díaz Cort, Josep; Serna Iglesias, María José; Thilikos Touloupas, Dimitrios (2002-03)
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Accés obert -
Recent results on parameterized H-coloring
Díaz Cort, Josep; Serna Iglesias, María José; Thilikos Touloupas, Dimitrios (2002-03)
Report de recerca
Accés obertWe survey recent results on the complexity of several versions of the H-coloring and the list-H-coloring problems that are amenable to parameterization. -
Smaller kernels for hitting set problems of constant arity
Nishimura, Naomi; Ragde, Prabhakar; Thilikos Touloupas, Dimitrios (2004-05)
Report de recerca
Accés obertWe demonstrate a kernel of size O(k^2) for 3-HITTING SET when all subsets in the collection to be hit are of size at most three), giving a partial answer to an open question of Niedermeier by improving on the O(k^3) ... -
Structure and enumeration of K4-minor-free links and link diagrams
Rué Perna, Juan José; Thilikos Touloupas, Dimitrios; Velona, Vasiliki (2018-07-01)
Article
Accés obertWe study the class L of link-types that admit a K4-minor-free diagram, i.e., they can be projected on the plane so that the resulting graph does not contain any subdivision of K4. We prove that L is the closure of a subclass ...