Given a positive integer k, a k-dominating set in a graph G is a set of vertices such that every vertex not in the set has at least k neighbors in the set. A total k-dominating set, also known as a k-tuple total domin...
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ISBN:
(纸本)9783319961514;9783319961507
Given a positive integer k, a k-dominating set in a graph G is a set of vertices such that every vertex not in the set has at least k neighbors in the set. A total k-dominating set, also known as a k-tuple total dominating set, is a set of vertices such that every vertex of the graph has at least k neighbors in the set. The problems of finding the minimum size of a k-dominating, resp. total k-dominating set, in a given graph, are referred to as k-domination, resp. total k-domination. These generalizations of the classical domination and total domination problems are known to be NP-hard in the class of chordal graphs, and, more specifically, even in the classes of split graphs (both problems) and undirected path graphs (in the case of total k-domination). On the other hand, it follows from recent work by Kang et al. (2017) that these two families of problems are solvable in time O(vertical bar V(G)vertical bar(6k+4)) in the class of interval graphs. In this work, we develop faster algorithms for k-domination and total k-domination in the class of proper interval graphs. The algorithms run in time O(vertical bar V(G)vertical bar(3k)) for each fixed k >= 1 and are also applicable to the weighted case.
A graph G is called a pairwise compatibility graph (PCG, for short) if it admits a tuple (T, w, d(min), d(max)) of a tree T whose leaf set is equal to the vertex set of G, a non-negative edge weight w, and two non-neg...
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ISBN:
(纸本)9783319947761;9783319947754
A graph G is called a pairwise compatibility graph (PCG, for short) if it admits a tuple (T, w, d(min), d(max)) of a tree T whose leaf set is equal to the vertex set of G, a non-negative edge weight w, and two non-negative reals d(min) <= d(max) such that G has an edge between two vertices u, v is an element of V if and only if the distance between the two leaves u and v in the weighted tree (T, w) is in the interval [d(min), d(max)]. The tree T is also called a witness tree of the PCG G. The problem of testing if a given graph is a PCG is not known to be NP -hard yet. To obtain a complete characterization of PCGs is a wide open problem in computational biology and graph theory. In the literature, most witness trees admitted by known PCGs are stars and caterpillars. In this paper, we give a complete characterization for a graph to be a star-PCG (a PCG that admits a star as its witness tree), which provides us the first polynomial-time algorithm for recognizing star-PCGs.
We. show that the chromatic number of {P-5, K-p - e}-free graphs can be computed in polynomialtime for each fixed p. Additionally, we prove polynomial-time solvability of the weighted vertex coloring problem for (P-5...
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We. show that the chromatic number of {P-5, K-p - e}-free graphs can be computed in polynomialtime for each fixed p. Additionally, we prove polynomial-time solvability of the weighted vertex coloring problem for (P-5, (P-3 + P-2) over bar}-free graphs. (C) 2016 Elsevier B.V. All rights reserved.
The present paper investigates Gaussian bilateral inequalities in view of solving related probability maximization problems. Since the function f representing the probability of satisfaction of a given Gaussian bilate...
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The present paper investigates Gaussian bilateral inequalities in view of solving related probability maximization problems. Since the function f representing the probability of satisfaction of a given Gaussian bilateral inequality is not concave everywhere, we first state and prove a necessary and sufficient condition for negative semi-definiteness of the Hessian. Then, the (nonconvex) problem of globally maximizing f over a given polyhedron in Rn is adressed, and shown to be polynomial-time solvable, thus yielding a new-comer to the (short) list of nonconvex global optimization problems which can be solved exactly in polynomialtime. Application to computing upper bounds to the maximum joint probability of satisfaction of a set of m independent Gaussian bilateral inequalities is discussed and computational results are reported.
A language is factorial if it is closed under taking factors, i.e. contiguous subwords. Every factorial language can be described by an antidictionary, i.e. a minimal set of forbidden factors. We show that the problem...
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A language is factorial if it is closed under taking factors, i.e. contiguous subwords. Every factorial language can be described by an antidictionary, i.e. a minimal set of forbidden factors. We show that the problem of deciding whether a factorial language given by a finite antidictionary is well-quasi-ordered under the factor containment relation can be solved in polynomialtime. We also discuss possible ways to extend our solution to permutations and graphs. (C) 2017 Elsevier Inc. All rights reserved.
Weighted independent domination is an NP-hard graph problem, which remains computationally intractable in many restricted graph classes. In particular, the problem is NP-hard in the classes of sat-graphs and chordal g...
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Weighted independent domination is an NP-hard graph problem, which remains computationally intractable in many restricted graph classes. In particular, the problem is NP-hard in the classes of sat-graphs and chordal graphs. We strengthen these results by showing that the problem is NP-hard in a proper subclass of the intersection of sat-graphs and chordal graphs. On the other hand, we identify two new classes of graphs where the problem admits polynomial-time solutions. (C) 2017 Elsevier B.V. All rights reserved.
The Hospitals / Residents problem with Couples (hrc) models the allocation of intending junior doctors to hospitals where couples are allowed to submit joint preference lists over pairs of (typically geographically cl...
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The Hospitals / Residents problem with Couples (hrc) models the allocation of intending junior doctors to hospitals where couples are allowed to submit joint preference lists over pairs of (typically geographically close) hospitals. It is known that a stable matching need not exist, so we consider min bp hrc, the problem of finding a matching that admits the minimum number of blocking pairs (i.e., is "as stable as possible"). We show that this problem is NP-hard and difficult to approximate even in the highly restricted case that each couple finds only one hospital pair acceptable. However if we further assume that the preference list of each single resident and hospital is of length at most 2, we give a polynomial-time algorithm for this case. We then present the first Integer Programming (IP) and Constraint Programming (CP) models for min bp hrc. Finally, we discuss an empirical evaluation of these models applied to randomly-generated instances of min bp hrc. We find that on average, the CP model is about 1.15 times faster than the IP model, and when presolving is applied to the CP model, it is on average 8.14 times faster. We further observe that the number of blocking pairs admitted by a solution is very small, i.e., usually at most 1, and never more than 2, for the (28,000) instances considered.
Binets and trinets are phylogenetic networks with two and three leaves, respectively. Here we consider the problem of deciding if there exists a binary level-1 phylogenetic network displaying a given set T of binary b...
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Binets and trinets are phylogenetic networks with two and three leaves, respectively. Here we consider the problem of deciding if there exists a binary level-1 phylogenetic network displaying a given set T of binary binets or trinets over a taxon set X, and constructing such a network whenever it exists. We show that this is NP-hard for trinets but polynomial-time solvable for binets. Moreover, we show that the problem is still polynomial-time solvable for inputs consisting of binets and trinets as long as the cycles in the trinets have size three. Finally, we present an O(3(vertical bar X vertical bar) poly(vertical bar X vertical bar)) timealgorithm for general sets of binets and trinets. The latter two algorithms generalise to instances containing level-1 networks with arbitrarily many leaves, and thus provide some of the first supernetwork algorithms for computing networks from a set of rooted phylogenetic networks.
This paper considers a multi-objective aircraft recovery problem for airline disruption. An integer programming formulation is first established based on connection network with three conflicting objectives, where the...
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This paper considers a multi-objective aircraft recovery problem for airline disruption. An integer programming formulation is first established based on connection network with three conflicting objectives, where the first objective minimizes the total deviation from original flight schedules, the second objective minimizes the maximal flight delay time, and the third objective minimizes the number of aircraft actually attended in swapping. Optimal analysis is provided for a small scale aircraft recovery problem with the last two objectives and then one polynomialtimealgorithm for aircraft recovery problem after the disruption to multi-aircraft in a fleet at an airport. One heuristic combined epsilon-constraints method and neighborhood search algorithm is designed for large scale disruption recovery problem. The results obtained from computational experiment illustrate effectiveness and efficiency of the heuristic. The outcome of this research could provide theoretical and practical supports for airlines to reduce flight delays. (C) 2017 Elsevier Ltd. All rights reserved.
In this paper, we investigate the Colourability problem for dually chordal graphs and some of its generalisations. We show that the problem remains NP-complete if limited to four colours. For the case of three colours...
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In this paper, we investigate the Colourability problem for dually chordal graphs and some of its generalisations. We show that the problem remains NP-complete if limited to four colours. For the case of three colours, we present a simple linear timealgorithm for dismantlable graphs (which include dually chordal graphs) and present an O(n(3)m) timealgorithm for graphs with tree-breadth 1. Additionally, we show that a dually chordal graph is 3-colourable if and only if it is perfect and has no clique of size four. (C) 2017 Elsevier B.V. All rights reserved.
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