In this paper, a set of intervals is constructed by projecting geometrical representation of permutation graph to find all cutvertices and blocks of a permutation graph. The sequential and parallel algorithms are desi...
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In this paper, a set of intervals is constructed by projecting geometrical representation of permutation graph to find all cutvertices and blocks of a permutation graph. The sequential and parallel algorithms are designed to find all cutvertices and blocks of permutation graphs. The sequential algorithms takes O(n) time and parallel algorithm takes O(log n) time using O(n/log n) processors on an EREW PRAM, where n represents the number of vertices of the graph.
The topology of an FDMA network is modeled by a subdivision of a planar region into hexagonal cells;this defines a graph where every node has at most six neighbors. For channel allocation, every node has a weight that...
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The topology of an FDMA network is modeled by a subdivision of a planar region into hexagonal cells;this defines a graph where every node has at most six neighbors. For channel allocation, every node has a weight that indicates the number of channels that must be assigned to it;the reuse distance defines the minimum distance between nodes that can use the same channel without radio interference. It is known that with reuse distance 2, the number of channels needed and their allocation can be approximated within a factor of 4/3 both offline and online. We describe an online algorithm for the case of reuse distance 3 that achieves an approximation factor of 7/3. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
The k-center problem with triangle inequality is that of placing k center nodes in a weighted undirected graph in which the edge weights obey the triangle inequality, so that the maximum distance of any node to its ne...
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The k-center problem with triangle inequality is that of placing k center nodes in a weighted undirected graph in which the edge weights obey the triangle inequality, so that the maximum distance of any node to its nearest center is minimized. In this paper, we consider a generalization of this problem where, given a number p, we wish to place k centers so as to minimize the maximum distance of any non-center node to its pth closest center. We derive a best possible approximation algorithm for this problem. (C) 1998 Elsevier Science B.V.
The graph sandwich problem for property Phi is defined as follows: Given two graphs G(1) = (V, E-1) and G(2) = (V, E-2) such that E-1 subset of or equal to E-2, is there a graph G = (V, E) such that E-1 subset of or e...
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The graph sandwich problem for property Phi is defined as follows: Given two graphs G(1) = (V, E-1) and G(2) = (V, E-2) such that E-1 subset of or equal to E-2, is there a graph G = (V, E) such that E-1 subset of or equal to E subset of or equal to E-2 which satisfies property Phi? We present a polynomial-time algorithm for solving the graph sandwich problem, when property Phi is "to contain a homogeneous set". The algorithm presented also provides the graph G and a homogeneous set in G in case it exists. (C) 1998 Elsevier Science B.V. All rights reserved.
We propose a combination of Kleene's three-valued logic and ACP process algebra via the guarded command construct. We present an operational semantics in SOS-style, and a completeness result. (C) 1998 Elsevier Sci...
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We propose a combination of Kleene's three-valued logic and ACP process algebra via the guarded command construct. We present an operational semantics in SOS-style, and a completeness result. (C) 1998 Elsevier Science B.V. All rights reserved.
Spin glasses represent one of the most challenging problems for solid state and statistical physics. The prototype of a spin glass is a dilute magnetic alloy. Many models have been proposed to describe the behavior ...
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Spin glasses represent one of the most challenging problems for solid state and statistical physics. The prototype of a spin glass is a dilute magnetic alloy. Many models have been proposed to describe the behavior of these systems. The Edwards-Anderson model, where elements are placed on the vertices of a regular lattice, the magnetic interactions hold only for nearest neighbors, and every element has only two states, is discussed. One of the interesting problems about this model is the determination of the minimal-energy states: the ground state (GS) problem. A new lower bound on the absolute error of polynomial-time approximation algorithms for the GS problem is presented.
Let a text string T of n symbols and a pattern string P of m symbols from alphabet Sigma be given. A swapped version T' of T is a length n string derived from T by a series of local swaps (i.e., t(iota)' <-...
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Let a text string T of n symbols and a pattern string P of m symbols from alphabet Sigma be given. A swapped version T' of T is a length n string derived from T by a series of local swaps (i.e., t(iota)' <-- t(iota+1) and t(iota+1)' <--t(iota)) where each element can participate in no more than one swap. The Pattern Matching with Swaps problem is that of finding all locations i for which there exists a swapped version T' of T where there is an exact matching of P at location i of T'. It was recently shown that the Pattern Matching with Swaps problem has a solution in time O(nm(1/3) log m log(2) sigma), where sigma = min(\Sigma\, m). We consider some interesting special cases of patterns, namely, patterns where there is no length-one run, i.e., there are no a, b, c epsilon Sigma where b not equal a and b not equal c and where the substring abe appears in the pattern. We show that for such patterns the Pattern Matching with Swaps problem can be solved in time O(n log(2) m). (C) 1998 Published by Elsevier Science B.V. All rights reserved.
Multipaging is the paging problem when more than one page can be requested at each step (Feuerstein, 1997). In the uniform cost model, a paging algorithm is charged for the number of pages loaded from disk to fast mem...
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Multipaging is the paging problem when more than one page can be requested at each step (Feuerstein, 1997). In the uniform cost model, a paging algorithm is charged for the number of pages loaded from disk to fast memory. In this note, we establish a general reduction from uniform multipaging to paging. As a consequence, we obtain the first strongly competitive randomized algorithm for uniform multipaging. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
Weight sequences were introduced by Pallo in 1986 for coding binary trees and he presented a constant amortized time algorithm for their generation in lexicographic order. A year later, Roelants van Baronaigien and Ru...
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Weight sequences were introduced by Pallo in 1986 for coding binary trees and he presented a constant amortized time algorithm for their generation in lexicographic order. A year later, Roelants van Baronaigien and Ruskey developed a recursive constant amortized time algorithm for generating Gray code for binary trees in Pallo's representation. It is common practice to find a loopless generating algorithm for a combinatorial object when enunciating a Gray code for this object. In this paper we regard weight sequences as variations and apply a Williamson algorithm in order to obtain a loopless generating algorithm for the Roelants van Baronaigien and Ruskey's Gray code for weight sequences. (C) 1998 Elsevier Science B.V. All rights reserved.
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