Algorithms for Destructive Shift Bribery
نویسندگان
چکیده
We study the complexity of Destructive Shift Bribery. In this problem, we are given an election with a set of candidates and a set of voters (ranking the candidates from best to worst, each), a despised candidate d (typically, one of the current winners), a budget B, and prices for shifting d down in voters’ rankings. The goal is to ensure that d is not a winner of the election. We show that this problem is polynomial-time solvable for all scoring protocols (encoded in unary) and the Maximin rule, but is NP-hard for the Copeland rule. This contrasts with the results for the constructive setting (known from the literature), for which the problem is polynomial-time solvable for k-Approval family of rules, but is NP-hard for the Borda, Copeland, and Maximin rules.
منابع مشابه
Complexity of Shift Bribery in Committee Elections
We study the (parameterized) complexity of SHIFT BRIBERY for multiwinner voting rules. We focus on the SNTV, Bloc, k-Borda, and Chamberlin-Courant, as well as on approximate variants of the Chamberlin-Courant rule, since the original rule is NP-hard to compute. We show that SHIFT BRIBERY tends to be significantly harder in the multiwinner setting than in the single-winner one by showing setting...
متن کاملLarge-Scale Election Campaigns: Combinatorial Shift Bribery
We study the complexity of a combinatorial variant of the Shift Bribery problem in elections. In the standard Shift Bribery problem, we are given an election where each voter has a preference order over the set of candidates and where an outside agent, the briber, can pay each voter to rank the briber’s favorite candidate a given number of positions higher. The goal is to ensure the victory of ...
متن کاملPrices Matter for the Parameterized Complexity of Shift Bribery
In the Shift Bribery problem, we are given an election (based on preference orders), a preferred candidate p, and a budget. The goal is to ensure p’s victory by shifting p higher in some voters’ preference orders. However, each such shift request comes at a price (depending on the voter and on the extent of the shift) and we must not exceed the given budget. We study the parameterized computati...
متن کاملThe Complexity of Control and Bribery in Majority Judgment
We study strategic voting problems for majority judgment, in which each voter assigns to every candidate a grade and the winners are determined by their majority-grades. We first study the constructive/destructive control by adding/deleting votes/candidates problems. Then we study the bribery problem, where an external agent wants to change the result by asking a limited number of voters to cha...
متن کاملThe Complexity of Bribery and Control in Group Identification
The goal of this paper is to analyze the complexity of bribery and destructive control in the framework of group identification. Group identification applies to situations where a group of individuals try to determine who among them are socially qualified for a given task. We consider consent rules, the consensus-start-respecting rule, and the liberalstart-respecting rule.
متن کامل