{"type":"ScholarlyArticle","title":"A Multivariate Complexity Analysis of Determining Possible Winners Given Incomplete Votes","authors":[{"name":"Nadja Betzler","slug":"nadja-betzler","given":"Nadja","family":"Betzler","affiliation":""},{"name":"Susanne Hemmann","slug":"susanne-hemmann","given":"Susanne","family":"Hemmann","affiliation":""},{"name":"Rolf Niedermeier","slug":"rolf-niedermeier","given":"Rolf","family":"Niedermeier","affiliation":""}],"abstract":"The Possible Winner problem asks whether some distinguished candidate may become the winner of an election when the given incomplete votes are extended into complete ones in a favorable way. Possible Winner is NP-complete for common voting rules such as Borda, many other positional scoring rules, Bucklin, Copeland etc. We investigate how three different parameterizations influence the computational complexity of Possible Winner for a number of voting rules. We show fixed-parameter tractability results with respect to the parameter number of candidates but intractability results with respect to the parameter number of votes. Finally, we derive fixed-parameter tractability results with respect to the parameter total number of undetermined candidate pairs and identify an interesting polynomial-time solvable special case for Borda.Nadja Betzler, Susanne Hemmann, Rolf Niedermeier","doi":null,"url":"https://ijcai.org/proceedings/2009/20","pdf":"https://ijcai.org/proceedings/2009/0020.pdf","markdown":"https://ijcai.org/proceedings/2009/20.md","bibtex":"https://ijcai.org/proceedings/2009/bibtex/20","volume":{"slug":"2009","title":"Proceedings of the Twenty-First International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2009","url":"https://ijcai.org/proceedings/2009/","year":2009,"location":"Pasadena, California, USA","dates":"","editors":"Hiroaki Kitano","isbn":"","publisher":"International Joint Conferences on Artificial Intelligence","doi_prefix":""},"section":null,"track":"","number":20,"pages":{"first":53,"last":57},"keywords":[],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}