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Schulze and ranked-pairs voting are fixed-parameter tractable to bribe, manipulate, and control

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Abstract

Schulze and ranked-pairs elections have received much attention recently, and the former has quickly become a quite widely used election system. For many cases these systems have been proven resistant to bribery, control, or manipulation, with ranked pairs being particularly praised for being NP-hard for all three of those. Nonetheless, the present paper shows that with respect to the number of candidates, Schulze and ranked-pairs elections are fixed-parameter tractable to bribe, control, and manipulate: we obtain uniform, polynomial-time algorithms whose running times’ degrees do not depend on the number of candidates. We also provide such algorithms for some weighted variants of these problems.

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Authors and Affiliations

  1. Department of Computer Science, University of Rochester, Rochester, NY, 14627, USA

    Lane A. Hemaspaandra & Rahman Lavaee

  2. Google Inc., Mountain View, CA, 94043, USA

    Curtis Menton

Authors
  1. Lane A. Hemaspaandra
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  2. Rahman Lavaee
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  3. Curtis Menton
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Correspondence to Lane A. Hemaspaandra.

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Hemaspaandra, L.A., Lavaee, R. & Menton, C. Schulze and ranked-pairs voting are fixed-parameter tractable to bribe, manipulate, and control. Ann Math Artif Intell 77, 191–223 (2016). https://doi.org/10.1007/s10472-015-9479-1

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  • DOI: https://doi.org/10.1007/s10472-015-9479-1

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