Hisao Tamaki | Meiji University (original) (raw)
Uploads
Papers by Hisao Tamaki
Bookmarks Related papers MentionsView impact
Journal of Combinatorial Optimization
Bookmarks Related papers MentionsView impact
Proceedings of the 20th International Symposium on Algorithms and Computation, 2009
ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pair... more ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pairs, called st-pairs, we consider the problems of finding an orientation of all edges in G: min-sum orientation is to minimize the sum of the shortest directed distances between all st-pairs; and min-max orientation is to minimize the maximum shortest directed distance among all st-pairs. In this paper, we first show that both problems are strongly NP-hard for planar graphs even if all edge-weights are identical, and that both problems can be solved in polynomial time for cycles. We then consider the problems restricted to cacti, which form a graph class that contains trees and cycles but is a subclass of planar graphs. Then, min-sum orientation is solvable in polynomial time, whereas min-max orientation remains NP-hard even for two st-pairs. However, based on LP-relaxation, we present a polynomial-time 2-approximation algorithm for min-max orientation. Finally, we give a fully polynomial-time approximation scheme (FPTAS) for min-max orientation on cacti if the number of st-pairs is a fixed constant.
Bookmarks Related papers MentionsView impact
Podc, 1993
Bookmarks Related papers MentionsView impact
Stoc, 1997
Bookmarks Related papers MentionsView impact
Interdisciplinary Information Sciences, 2000
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Fgcs, 1984
ABSTRACT
Bookmarks Related papers MentionsView impact
Algorithmica, 2002
ABSTRACT
Bookmarks Related papers MentionsView impact
Ieice Transactions on Information and Systems, Mar 25, 2000
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
2010 10th International Symposium on Communications and Information Technologies, 2010
Bookmarks Related papers MentionsView impact
Proceedings of the fourth annual ACM symposium on Parallel algorithms and architectures - SPAA '92, 1992
Bookmarks Related papers MentionsView impact
Lecture Notes in Computer Science, 2003
Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the ... more Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the bipartite graph on the sets of vertices and of faces of G such that each of its edges represents an incidence in G between a face and a vertex. Let α G denote the maximum distance in VF(G) from the outerface of G.
Bookmarks Related papers MentionsView impact
Lecture Notes in Computer Science, 2011
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Lecture Notes in Computer Science, 2015
Bookmarks Related papers MentionsView impact
Interdisciplinary Information Sciences, 2000
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Journal of Combinatorial Optimization
Bookmarks Related papers MentionsView impact
Proceedings of the 20th International Symposium on Algorithms and Computation, 2009
ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pair... more ABSTRACT Given an undirected and edge-weighted graph G together with a set of ordered vertex-pairs, called st-pairs, we consider the problems of finding an orientation of all edges in G: min-sum orientation is to minimize the sum of the shortest directed distances between all st-pairs; and min-max orientation is to minimize the maximum shortest directed distance among all st-pairs. In this paper, we first show that both problems are strongly NP-hard for planar graphs even if all edge-weights are identical, and that both problems can be solved in polynomial time for cycles. We then consider the problems restricted to cacti, which form a graph class that contains trees and cycles but is a subclass of planar graphs. Then, min-sum orientation is solvable in polynomial time, whereas min-max orientation remains NP-hard even for two st-pairs. However, based on LP-relaxation, we present a polynomial-time 2-approximation algorithm for min-max orientation. Finally, we give a fully polynomial-time approximation scheme (FPTAS) for min-max orientation on cacti if the number of st-pairs is a fixed constant.
Bookmarks Related papers MentionsView impact
Podc, 1993
Bookmarks Related papers MentionsView impact
Stoc, 1997
Bookmarks Related papers MentionsView impact
Interdisciplinary Information Sciences, 2000
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Fgcs, 1984
ABSTRACT
Bookmarks Related papers MentionsView impact
Algorithmica, 2002
ABSTRACT
Bookmarks Related papers MentionsView impact
Ieice Transactions on Information and Systems, Mar 25, 2000
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
2010 10th International Symposium on Communications and Information Technologies, 2010
Bookmarks Related papers MentionsView impact
Proceedings of the fourth annual ACM symposium on Parallel algorithms and architectures - SPAA '92, 1992
Bookmarks Related papers MentionsView impact
Lecture Notes in Computer Science, 2003
Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the ... more Let G be a biconnected planar graph given together with its planar drawing. Let VF(G) denote the bipartite graph on the sets of vertices and of faces of G such that each of its edges represents an incidence in G between a face and a vertex. Let α G denote the maximum distance in VF(G) from the outerface of G.
Bookmarks Related papers MentionsView impact
Lecture Notes in Computer Science, 2011
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Lecture Notes in Computer Science, 2015
Bookmarks Related papers MentionsView impact
Interdisciplinary Information Sciences, 2000
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact