共查询到20条相似文献,搜索用时 15 毫秒
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《Journal of Computer and System Sciences》2016,82(5):802-816
The rotor-router mechanism was introduced as a deterministic alternative to the random walk in undirected graphs. In this model, a set of k identical walkers is deployed in parallel, starting from a chosen subset of nodes, and moving around the graph in synchronous steps. During the process, each node successively propagates walkers visiting it along its outgoing arcs in round-robin fashion, according to a fixed ordering. We consider the cover time of such a system, i.e., the number of steps after which each node has been visited by at least one walk, regardless of the initialization of the walks. We show that for any graph with m edges and diameter D, this cover time is at most and at least , which corresponds to a speedup of between and with respect to the cover time of a single walk. 相似文献
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《Journal of Computer and System Sciences》2016,82(5):793-801
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《Journal of Computer and System Sciences》2016,82(5):782-792
This paper presents improved algorithms for the round-trip single-facility location problem on a general graph, in which a set A of collection depots is given and the service distance of a customer is defined to be the distance from the server, to the customer, then to a depot, and back to the server. Each customer i is associated with a subset of depots that i can potentially select from and use. When for each customer i, the problem is unrestricted; otherwise it is restricted. For the restricted round-trip 1-center problem, we give an -time algorithm. For the restricted 1-median problem, we give an -time algorithm. For the unrestricted 1-median problem, we give an -time algorithm. 相似文献
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Jian Wang Xirong Xu Dejun Zhu Liqing Gao Jun-Ming Xu 《Information Processing Letters》2012,112(12):473-478
The feedback number of a graph G is the minimum number of vertices whose removal from G results in an acyclic subgraph. We use to denote the feedback number of the -star graph and the number of k-permutations of an n-element set. This paper proves that where . 相似文献
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Let be a connected graph on n vertices. The proximity of G is the minimum average distance from a vertex of G to all others. The eccentricity of a vertex v in G is the largest distance from v to another vertex, and the average eccentricity of the graph G is . Recently, it was conjectured by Aouchiche and Hansen (2011) [3] that for any connected graph G on vertices, , with equality if and only if . In this paper, we show that this conjecture is true. 相似文献
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In multiple-instance learning the learner receives bags, i.e., sets of instances. A bag is labeled positive if it contains a positive example of the target. An lower bound is given for the VC-dimension of bags of size r for d-dimensional halfspaces and it is shown that the same lower bound holds for halfspaces over any large point set in general position. This lower bound improves an lower bound of Sabato and Tishby, and it is sharp in order of magnitude. We also show that the hypothesis finding problem is NP-complete and formulate several open problems. 相似文献
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