Computers and Intractability: A Guide to the Theory of NP-Completeness
Computers and Intractability: A Guide to the Theory of NP-Completeness
Anyone but him: The complexity of precluding an alternative
Artificial Intelligence
Vote manipulation in the presence of multiple sincere ballots
TARK '07 Proceedings of the 11th conference on Theoretical aspects of rationality and knowledge
Sincere-Strategy Preference-Based Approval Voting Broadly Resists Control
MFCS '08 Proceedings of the 33rd international symposium on Mathematical Foundations of Computer Science
Towards a Dichotomy of Finding Possible Winners in Elections Based on Scoring Rules
MFCS '09 Proceedings of the 34th International Symposium on Mathematical Foundations of Computer Science 2009
Determining possible and necessary winners under common voting rules given partial orders
AAAI'08 Proceedings of the 23rd national conference on Artificial intelligence - Volume 1
Complexity of strategic behavior in multi-winner elections
Journal of Artificial Intelligence Research
Incompleteness and incomparability in preference aggregation
IJCAI'07 Proceedings of the 20th international joint conference on Artifical intelligence
Llull and Copeland voting computationally resist bribery and constructive control
Journal of Artificial Intelligence Research
A multivariate complexity analysis of determining possible winners given incomplete votes
IJCAI'09 Proceedings of the 21st international jont conference on Artifical intelligence
Preference functions that score rankings and maximum likelihood estimation
IJCAI'09 Proceedings of the 21st international jont conference on Artifical intelligence
Multimode control attacks on elections
IJCAI'09 Proceedings of the 21st international jont conference on Artifical intelligence
Using complexity to protect elections
Communications of the ACM
Taking the Final Step to a Full Dichotomy of the Possible Winner Problem in Pure Scoring Rules
Proceedings of the 2010 conference on ECAI 2010: 19th European Conference on Artificial Intelligence
Compilation and communication protocols for voting rules with a dynamic set of candidates
Proceedings of the 13th Conference on Theoretical Aspects of Rationality and Knowledge
Determining possible and necessary winners under common voting rules given partial orders
Journal of Artificial Intelligence Research
Taking the final step to a full dichotomy of the possible winner problem in pure scoring rules
Information Processing Letters
Cloning in elections: finding the possible winners
Journal of Artificial Intelligence Research
Campaigns for lazy voters: truncated ballots
Proceedings of the 11th International Conference on Autonomous Agents and Multiagent Systems - Volume 2
Possible and necessary winners of partial tournaments
Proceedings of the 11th International Conference on Autonomous Agents and Multiagent Systems - Volume 2
Control in the presence of manipulators: cooperative and competitive cases
IJCAI'13 Proceedings of the Twenty-Third international joint conference on Artificial Intelligence
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In a voting system, sometimes multiple new alternatives will join the election after the voters' preferences over the initial alternatives have been revealed. Computing whether a given alternative can be a co-winner when multiple new alternatives join the election is called the possible co-winner with new alternatives (PcWNA) problem and was introduced by Chevaleyre et al. 6]. In this paper, we show that the PcWNA problems are NP-complete for the Bucklin, Copeland0, and maximin (a.k.a. Simpson) rule, even when the number of new alternatives is no more than a constant. We also show that the PcWNA problem can be solved in polynomial time for plurality with runoff. For the approval rule, we examine three different ways to extend a linear order with new alternatives, and characterize the computational complexity of the PcWNA problem for each of them.