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Algorithms and Computation (ISAAC 2012)
Theoretical Computer Science 544 (2014) 1–2
Contents lists available at ScienceDirect
Theoretical Computer Science www.elsevier.com/locate/tcs
Preface
Algorithms and Computation (ISAAC 2012) This special issue of Theoretical Computer Science contains extended versions of selected contributions to The 23rd International Symposium on Algorithms and Computation (ISAAC 2012) held in Taipei, Taiwan, on December 19–21, 2012. The mission of the ISAAC series is to provide a top-notch forum for researchers working in algorithms and theory of computation. The ISAAC 2012 Program Committee selected 68 papers for oral presentation out of 174 high-quality submissions from 33 countries. Among those presented papers, the following seven papers in the theory of computation have been selected in this special issue. They went through a standard review process of Theoretical Computer Science. The paper Popular and Clan-Popular b-Matchings by Katarzyna Paluch provides a characterization of popular b-matchings and proves that the popular b-matching problem is NP-hard. The author also shows that finding a clan-popular (many-tomany) b-matching or reporting that it does not exist is NP-hard. Some polynomial algorithms are given for certain restricted cases. The paper A 4.31-Approximation for the Geometric Unique Coverage Problem on Unit Disks by Takehiro Ito, Shin-ichi Nakano, Yoshio Okamoto, Yota Otachi, Ryuhei Uehara, Takeaki Uno, and Yushi Uno gives an improved approximation algorithm for the unique unit-disk coverage problem, which is to find a subset of disks that maximizes the number √ of points contained in exactly one disk in the subset. The authors improve the approximation ratio from 18 to 2 + 4/ 3 + ε (< 4.3095 + ε ) for any fixed constant ε > 0. Their algorithm runs in polynomial time depending exponentially on 1/ε and can be generalized to the budgeted unique unit-disk coverage problem. The paper On the Number of Upward Planar Orientations of Maximal Planar Graphs by Fabrizio Frati, Joachim Gudmundsson, and Emo Welzl proves that every n-vertex maximal planar graph has at least Ω ∗ (1.189n ) and at most O ∗ (4n ) upward planar orientations. Moreover, the authors show that there exist n-vertex maximal planar graphs having O ∗ (2n ) upward planar orientations and n-vertex maximal planar graphs having Ω ∗ (2.599n ) upward planar orientations. They also present bounds for the maximum and the minimum number of acyclic orientations that a maximal planar graph can have. The publisher regrets to inform that the following paper Revenue Maximization in a Bayesian Double Auction Market by Xiaotie Deng, Paul Goldberg, Bo Tang, and Jinshan Zhang was published in a regular issue due to a technical error. The article was instead published in the issue: Theoretical Computer Science, Volume 539. We apologize for this error. Please find below the article title, author details and link to the article: Revenue maximization in a Bayesian double auction market Xiaotie Denga , Paul Goldbergb , Bo Tangc , Jinshan Zhangc a Department of Computer Science, Shanghai Jiao Tong University, China b Department of Computer Science, University of Oxford, United Kingdom c Department of Computer Science, University of Liverpool, United Kingdom http://www.sciencedirect.com/science/article/pii/S0304397514002928 The paper Efficient Counting of Square Substrings in a Tree by Tomasz Kociumaka, Jakub Pachocki, Jakub Radoszewski, Wojciech Rytter, and Tomasz Wale´ n considers square substrings corresponding to simple paths in labeled unrooted trees. The authors give an algorithm which in O (n log2 n) time counts all distinct squares in a labeled tree with n nodes. They also provide a compact representation of the set of all distinct squares. The paper Abstract Flows over Time: A First Step towards Solving Dynamic Packing Problems by Jan-Philipp W. Kappmeier, Jannik Matuschke, and Britta Peis introduces a new concept called abstract flows over time. The authors show how a temporally repeated abstract flow and a corresponding minimum cut can be computed by solving a single static weighted abstract flow problem. They also derive some interesting structural properties of abstract networks and show that the relatively modest switching property of abstract networks already captures many essential properties of classic networks. The paper Reconfiguration of List L (2, 1)-Labelings in a Graph by Takehiro Ito, Kazuto Kawamura, Hirotaka Ono, and Xiao Zhou studies the problem of reconfiguring one list L (2, 1)-labeling of a graph into another list L (2, 1)-labeling of the same graph by changing only one label at a time, while at all times maintaining a list L (2, 1)-labeling. The authors show that its decision http://dx.doi.org/10.1016/j.tcs.2014.06.034 0304-3975/© 2014 Published by Elsevier B.V.
2
Preface
version is PSPACE-complete, even for some restricted cases. On the other hand, they show that the problem can be solved in linear time for general graphs with at most five different labels. They further give a sufficient condition for which any two list L (2, 1)-labelings of a tree can be transformed into each other. We wish to thank all authors and anonymous referees for their great contribution.
Kun-Mao Chao National Taiwan University, Taipei, 106, Taiwan E-mail address: [email protected] Tsan-sheng Hsu Academia Sinica, Taipei, 115, Taiwan E-mail address: [email protected] D.T. Lee National Chung Hsing University, Taichung, 402, Taiwan E-mail address: [email protected]
Contents lists available at ScienceDirect
Theoretical Computer Science www.elsevier.com/locate/tcs
Preface
Algorithms and Computation (ISAAC 2012) This special issue of Theoretical Computer Science contains extended versions of selected contributions to The 23rd International Symposium on Algorithms and Computation (ISAAC 2012) held in Taipei, Taiwan, on December 19–21, 2012. The mission of the ISAAC series is to provide a top-notch forum for researchers working in algorithms and theory of computation. The ISAAC 2012 Program Committee selected 68 papers for oral presentation out of 174 high-quality submissions from 33 countries. Among those presented papers, the following seven papers in the theory of computation have been selected in this special issue. They went through a standard review process of Theoretical Computer Science. The paper Popular and Clan-Popular b-Matchings by Katarzyna Paluch provides a characterization of popular b-matchings and proves that the popular b-matching problem is NP-hard. The author also shows that finding a clan-popular (many-tomany) b-matching or reporting that it does not exist is NP-hard. Some polynomial algorithms are given for certain restricted cases. The paper A 4.31-Approximation for the Geometric Unique Coverage Problem on Unit Disks by Takehiro Ito, Shin-ichi Nakano, Yoshio Okamoto, Yota Otachi, Ryuhei Uehara, Takeaki Uno, and Yushi Uno gives an improved approximation algorithm for the unique unit-disk coverage problem, which is to find a subset of disks that maximizes the number √ of points contained in exactly one disk in the subset. The authors improve the approximation ratio from 18 to 2 + 4/ 3 + ε (< 4.3095 + ε ) for any fixed constant ε > 0. Their algorithm runs in polynomial time depending exponentially on 1/ε and can be generalized to the budgeted unique unit-disk coverage problem. The paper On the Number of Upward Planar Orientations of Maximal Planar Graphs by Fabrizio Frati, Joachim Gudmundsson, and Emo Welzl proves that every n-vertex maximal planar graph has at least Ω ∗ (1.189n ) and at most O ∗ (4n ) upward planar orientations. Moreover, the authors show that there exist n-vertex maximal planar graphs having O ∗ (2n ) upward planar orientations and n-vertex maximal planar graphs having Ω ∗ (2.599n ) upward planar orientations. They also present bounds for the maximum and the minimum number of acyclic orientations that a maximal planar graph can have. The publisher regrets to inform that the following paper Revenue Maximization in a Bayesian Double Auction Market by Xiaotie Deng, Paul Goldberg, Bo Tang, and Jinshan Zhang was published in a regular issue due to a technical error. The article was instead published in the issue: Theoretical Computer Science, Volume 539. We apologize for this error. Please find below the article title, author details and link to the article: Revenue maximization in a Bayesian double auction market Xiaotie Denga , Paul Goldbergb , Bo Tangc , Jinshan Zhangc a Department of Computer Science, Shanghai Jiao Tong University, China b Department of Computer Science, University of Oxford, United Kingdom c Department of Computer Science, University of Liverpool, United Kingdom http://www.sciencedirect.com/science/article/pii/S0304397514002928 The paper Efficient Counting of Square Substrings in a Tree by Tomasz Kociumaka, Jakub Pachocki, Jakub Radoszewski, Wojciech Rytter, and Tomasz Wale´ n considers square substrings corresponding to simple paths in labeled unrooted trees. The authors give an algorithm which in O (n log2 n) time counts all distinct squares in a labeled tree with n nodes. They also provide a compact representation of the set of all distinct squares. The paper Abstract Flows over Time: A First Step towards Solving Dynamic Packing Problems by Jan-Philipp W. Kappmeier, Jannik Matuschke, and Britta Peis introduces a new concept called abstract flows over time. The authors show how a temporally repeated abstract flow and a corresponding minimum cut can be computed by solving a single static weighted abstract flow problem. They also derive some interesting structural properties of abstract networks and show that the relatively modest switching property of abstract networks already captures many essential properties of classic networks. The paper Reconfiguration of List L (2, 1)-Labelings in a Graph by Takehiro Ito, Kazuto Kawamura, Hirotaka Ono, and Xiao Zhou studies the problem of reconfiguring one list L (2, 1)-labeling of a graph into another list L (2, 1)-labeling of the same graph by changing only one label at a time, while at all times maintaining a list L (2, 1)-labeling. The authors show that its decision http://dx.doi.org/10.1016/j.tcs.2014.06.034 0304-3975/© 2014 Published by Elsevier B.V.
2
Preface
version is PSPACE-complete, even for some restricted cases. On the other hand, they show that the problem can be solved in linear time for general graphs with at most five different labels. They further give a sufficient condition for which any two list L (2, 1)-labelings of a tree can be transformed into each other. We wish to thank all authors and anonymous referees for their great contribution.
Kun-Mao Chao National Taiwan University, Taipei, 106, Taiwan E-mail address: [email protected] Tsan-sheng Hsu Academia Sinica, Taipei, 115, Taiwan E-mail address: [email protected] D.T. Lee National Chung Hsing University, Taichung, 402, Taiwan E-mail address: [email protected]