We provide an algorithm for listing all minimal 2-dominating sets of a tree of order n in time O(1.3248(n)). This implies that every tree has at most 1.3248(n) minimal 2-dominating sets. We also show that this bound i...
详细信息
We provide an algorithm for listing all minimal 2-dominating sets of a tree of order n in time O(1.3248(n)). This implies that every tree has at most 1.3248(n) minimal 2-dominating sets. We also show that this bound is tight.
We give an algorithm for computing the directed pathwidth of a digraph with n vertices in O(1.89(n)) time. This is the first algorithm with running time better than the straightforward O*(2(n)). As a special case, it ...
详细信息
We give an algorithm for computing the directed pathwidth of a digraph with n vertices in O(1.89(n)) time. This is the first algorithm with running time better than the straightforward O*(2(n)). As a special case, it computes the pathwidth of an undirected graph in the same amount of time, improving on the algorithm due to Suchan and Villanger which runs in O(1.9657(n)) time.
We prove that for any epsilon > 0 there exists an integer n(epsilon) such that the pathwidth of every cubic (or 3-regular) graph on n > n(epsilon) vertices is at most (1/6 + epsilon)n. Based on this bound we imp...
详细信息
We prove that for any epsilon > 0 there exists an integer n(epsilon) such that the pathwidth of every cubic (or 3-regular) graph on n > n(epsilon) vertices is at most (1/6 + epsilon)n. Based on this bound we improve the worst case time analysis for a number of exact exponential algorithms on graphs of maximum vertex degree three. (c) 2005 Elsevier B.V. All rights reserved.
The paper presents an -time and polynomial-space algorithm for the traveling salesman problem in an -vertex graph with maximum degree 3. This improves all previous time bounds of polynomial-space algorithms for this p...
详细信息
The paper presents an -time and polynomial-space algorithm for the traveling salesman problem in an -vertex graph with maximum degree 3. This improves all previous time bounds of polynomial-space algorithms for this problem. Our algorithm is a simple branch-and-search algorithm with only one branch rule designed on a cut-circuit structure of a graph induced by unprocessed edges. To improve a time bound by a simple analysis on measure and conquer, we introduce an amortization scheme over the cut-circuit structure by defining the measure of an instance to be the sum of not only weights of vertices but also weights of connected components of the induced graph.
Inclusion/exclusion and measure and conquer are two central techniques from the field of exactexponential-time algorithms that recently received a lot of attention. In this paper, we show that both techniques can be ...
详细信息
Inclusion/exclusion and measure and conquer are two central techniques from the field of exactexponential-time algorithms that recently received a lot of attention. In this paper, we show that both techniques can be used in a single algorithm. This is done by looking at the principle of inclusion/exclusion as a branching rule. This inclusion/exclusion-based branching rule can be combined in a branch-and-reduce algorithm with traditional branching rules and reduction rules. The resulting algorithms can be analysed using measure and conquer allowing us to obtain good upper bounds on their running times. In this way, we obtain the currently fastest exactexponential-time algorithms for a number of domination problems in graphs. Among these are faster polynomial-space and exponential-space algorithms for #Dominating Set and Minimum Weight Dominating Set (for the case where the set of possible weight sums is polynomially bounded), and a faster polynomial-space algorithm for Domatic Number. This approach is also extended in this paper to the setting where not all requirements in a problem need to be satisfied. This results in faster polynomial-space and exponential-space algorithms for Partial Dominating Set, and faster polynomial-space and exponential-space algorithms for the well-studied parameterised problem k-Set Splitting and its generalisation k-Not-All-Equal Satisfiability.
The family of stable matching problems have been well-studied across a wide field of research areas, including economics, mathematics and computer science. In general, an instance of a stable matching problem is given...
详细信息
The family of stable matching problems have been well-studied across a wide field of research areas, including economics, mathematics and computer science. In general, an instance of a stable matching problem is given by a set of participants who have expressed their preferences of each other, and asks to find a "stable" matching, that is, a pairing of the participants such that no unpaired participants prefer each other to their assigned partners. In the case of the Stable Roommates Problem (SR), it is known that given an even number n of participants, there might not exist a stable matching that pairs all of the participants, but there exist efficient algorithms to determine if this is possible or not, and if it is possible, produce such a matching. Common extensions of SR allow for the participants' preference lists to be incomplete, or include indifference. Allowing indifference in turn, gives rise to different possible definitions of stability, super, strong, and weak stability. While instances asking for super and strongly stable matching can be efficiently solved even if preference lists are incomplete, the case of weak stability is NP-complete. We examine a restricted case of indifference, introducing the concept of unranked entries. For this type of instances, we show that the problem of finding a weakly stable matching remains NP-complete even if each participant has a complete preference list with at most two unranked entries, or is herself unranked for up to three other participants. On the other hand, for instances where there are m acceptable pairs and there are in total k unranked entries in all of the participants' preference lists, we propose an O(2(k)n(2))-time and polynomial space algorithm that finds a stable matching, or determines that none exists in the given instance.
The circuit satisfiability problem has been intensively studied since Ryan Williams showed a connection between the problem and lower bounds for circuit complexity. In this letter, we present a #SAT algorithm for sync...
详细信息
The circuit satisfiability problem has been intensively studied since Ryan Williams showed a connection between the problem and lower bounds for circuit complexity. In this letter, we present a #SAT algorithm for synchronous Boolean circuits of n inputs and s gates in time 2(n(1 - 1/2O(s/n))) if s = o(n log n).
We provide an algorithm for listing all minimal double dominating sets of a tree of order n in time O(1.3248(n)). This implies that every tree has at most 1.3248(n) minimal double dominating sets. We also show that th...
详细信息
ISBN:
(纸本)9783319080161;9783319080154
We provide an algorithm for listing all minimal double dominating sets of a tree of order n in time O(1.3248(n)). This implies that every tree has at most 1.3248(n) minimal double dominating sets. We also show that this bound is tight.
This paper presents the first polynomial-space exactalgorithm specialized for the TSP in graphs with degree at most 6. We develop a set of branching rules to aid the analysis of the branching algorithm. Using the mea...
详细信息
ISBN:
(纸本)9783319485324;9783319485317
This paper presents the first polynomial-space exactalgorithm specialized for the TSP in graphs with degree at most 6. We develop a set of branching rules to aid the analysis of the branching algorithm. Using the measure-and-conquer method, we show that when applied to an n-vertex graph with degree at most 6, the algorithm has a running time of O*(3.0335(n)), which is still advantageous over other known polynomial-space algorithms for the TSP in general graphs.
The problem of finding a minimum feedback vertex set has many applications and its history can be traced back to the early '60s (see the survey of Festa at al. [2]). It is also one of the classical NP-complete pro...
详细信息
ISBN:
(纸本)3540390987
The problem of finding a minimum feedback vertex set has many applications and its history can be traced back to the early '60s (see the survey of Festa at al. [2]). It is also one of the classical NP-complete problems from Karp's list [5]. There is quite a dramatic story of obtaining faster and faster parameterized algorithms with a chain of improvements (see e.g. [7]) concluding with 2(O(k))n(O(1))-time algorithms obtained independently by different research groups [1,4]. A feedback vertex set of a graph on n vertices can be trivially found in time 0(2 n n) by trying all possible vertex subsets. For a long time, despite attacks of many researchers, no faster exponential time algorithm was known. Very recently Razgon [8] broke the 2(n) barrier with an O(1.8899(n)) time algorithm. The algorithm of Razgon is based on the Branch & Reduce paradigm and its analysis is nice and clever. In this paper we show how to find a minimum feedback vertex set in time O(1.7548(n)). Our improvement is based on Razgon's idea of measuring the progress of the branching algorithm. The most significant improvement in the running time of our algorithm is due to a new branching rule which is based on Proposition 2. This rule works nicely except one case, which, luckily, can be reduced to finding an independent set of maximum size.
暂无评论