We present an output sensitive algorithm for computing a maximum independent set of an unweighted circle graph. Our algorithm requires O(n min{d,alpha}) time at worst, for an n vertex circle graph where a is the indep...
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We present an output sensitive algorithm for computing a maximum independent set of an unweighted circle graph. Our algorithm requires O(n min{d,alpha}) time at worst, for an n vertex circle graph where a is the independence number of the circle graph and d is its density. Previous algorithms for this problem required Theta(nd) time at worst. (C) 2010 Elsevier B.V. All rights reserved.
The rotation distance d(S, T) between two binary trees S, T of n vertices is the minimum number of rotations to transform S into T. While it is known that d(S, T) = 11. We are unable to prove the conjecture, but we gi...
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The rotation distance d(S, T) between two binary trees S, T of n vertices is the minimum number of rotations to transform S into T. While it is known that d(S, T) <= 2n - 6, a well-known conjecture states that there are trees for which this bound is sharp for any value of n >= 11. We are unable to prove the conjecture, but we give here some simple criteria for lower bound evaluation, leading for example to individuate some "regular" tree structures for which d(S, T) = 3n/2 - O(1), or d(S, T) = 5n/3 - O(1). (C) 2010 Elsevier B.V. All rights reserved.
The Floyd-Warshall algorithm is a simple and widely used algorithm to compute shortest paths between all pairs of vertices in an edge weighted directed graph. It can also be used to detect the presence of negative cyc...
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The Floyd-Warshall algorithm is a simple and widely used algorithm to compute shortest paths between all pairs of vertices in an edge weighted directed graph. It can also be used to detect the presence of negative cycles. We will show that for this task many existing implementations of the Floyd-Warshall algorithm will fail because exponentially large numbers can appear during its execution. (C) 2010 Elsevier B.V. All rights reserved.
The design of many tail recursive algorithms can involve thinking about the status of variables and parameters, and how these change with execution flow. In other words, tail recursion is closely related to iteration ...
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ISBN:
(纸本)9781605588209
The design of many tail recursive algorithms can involve thinking about the status of variables and parameters, and how these change with execution flow. In other words, tail recursion is closely related to iteration and imperative programming. However, it is possible to derive tail recursive functions by exclusively using concepts inherent in recursion, such as declarative programming, induction, or problem decomposition. This paper proposes a simple methodology for designing tail recursion functions by using a declarative approach and the concept of function generalization. We have carried out an evaluation of the technique with second and third-year computer science students. Results suggest that this new point of view improves students' ability to design tail recursive programs, helps them understand the distinction between the imperative and declarative paradigms, and may reinforce their programming skills in general. Furthermore, students found the methodology easy to learn and apply, simpler than more sophisticated formal methods, and described it as fast and methodic or mechanical, as it involves a sequence of well-defined steps.
In this paper, we address the problem on video matting of natural snow in snowing context. By optical features of natural snow and the continuity of a video, we design a suitable temporal filter to recover the backgro...
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In this paper, we address the problem on video matting of natural snow in snowing context. By optical features of natural snow and the continuity of a video, we design a suitable temporal filter to recover the background of the video and compute the approximate matte gradient. Using two types of information obtained, we first propose a closed-form solution to video matting of natural snow. (C) 2009 Elsevier B.V. All rights reserved.
In this paper we consider the problem of computing an "optimal" popular matching. We assume that our input instance G = (A boolean OR P, E-1 (boolean OR) over dot ... (boolean OR) over dot E-r) admits a popu...
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In this paper we consider the problem of computing an "optimal" popular matching. We assume that our input instance G = (A boolean OR P, E-1 (boolean OR) over dot ... (boolean OR) over dot E-r) admits a popular matching and here we are asked to return not any popular matching but an optimal popular matching, where the definition of optimality is given as a part of the problem statement;for instance, optimality could be fairness in which case we are required to return a fair popular matching. We show an O(n(2) + m) algorithm for this problem, assuming that the preference lists are strict, where m is the number of edges in G and n is the number of applicants. (C) 2009 Elsevier B.V. All rights reserved.
Batching has been studied extensively in the offline case, but applications such as manufacturing or TCP acknowledgment often require online solutions. We consider online batching problems, where the order of jobs to ...
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Batching has been studied extensively in the offline case, but applications such as manufacturing or TCP acknowledgment often require online solutions. We consider online batching problems, where the order of jobs to be hatched is fixed and where we seek to minimize the sum of the completion times of the jobs. We present optimally competitive online algorithms for both s-batch and p-batch problems, and we also derive results for certain naturally Occurring special cases, such as the case of unit processing times. (C) 2009 Elsevier B.V. All rights reserved.
Monotonicity is a simple yet significant qualitative characteristic. We consider the problem of segmenting a sequence in up to K segments. We want the segments to be as monotonic as possible and to alternate signs. We...
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Monotonicity is a simple yet significant qualitative characteristic. We consider the problem of segmenting a sequence in up to K segments. We want the segments to be as monotonic as possible and to alternate signs. We propose a quality metric for this problem using the l norm, and we present an optimal linear time algorithm based on a novel formalism. Moreover, given a precomputation in time O(n log n) consisting of a labelling of all extrema, we compute any optimal segmentation in constant time. We compare experimentally its performance to two piecewise linear segmentation heuristics (top-down and bottom-up). We show that our algorithm is faster and more accurate. Applications include pattern recognition and qualitative modelling.
With the rapid advances in communication and networking, especially in Grid technique, an increasing number of applications will involve computing systems. These applications in turn create an increasing demand for ef...
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With the rapid advances in communication and networking, especially in Grid technique, an increasing number of applications will involve computing systems. These applications in turn create an increasing demand for efficient resource management, request handling policies and access control. In this paper, we propose an efficient access control algorithm to protect the critical resource of server and improve the performance of the future grid communication computing system. Stability of CPU utilization is aimed to protect the server from overload and under-load. It is then beneficial to keep a satisfactory response time of requests, high throughput and less potential loss of service. We analyze the stability in detail and present a method for tuning control gains in order to guarantee the system stability. Finally, we perform simulations to evaluate the performance of the proposed algorithm. Simulation results demonstrate that the proposed algorithm stabilizes the utilization of CPU in the computing system if the control gains are appropriately chosen on the basis of system stability. It then achieves satisfactory performance.
String inclusion and non-inclusion problems have been vigorously studied in such diverse fields as molecular biology, data compression, and computer security. Among the well-known string inclusion or non-inclusion not...
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String inclusion and non-inclusion problems have been vigorously studied in such diverse fields as molecular biology, data compression, and computer security. Among the well-known string inclusion or non-inclusion notions, we are interested in the longest common nonsuperstring. Given a set of strings, the longest common nonsuperstring problem is finding the longest string that is not a superstring of any string in the given set. It is known that the longest common nonsuperstring problem is solvable in polynomial time. In this paper, we propose an efficient algorithm for the longest common nonsuperstring problem. The running time of our algorithm is linear with respect to the sum of the lengths of the strings in the given set, using generalized suffix trees. (C) 2009 Elsevier B.V. All rights reserved.
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