Exact 3-Satisfiability Is Decidable in Time O(20.16254n)

  • Authors:
  • Stefan Porschen;Bert Randerath;Ewald Speckenmeyer

  • Affiliations:
  • Institut für Informatik, Universität zu Köln, 50969 Köln, Germany E-mail: porschen@informatik.uni-koeln.de;Institut für Informatik, Universität zu Köln, 50969 Köln, Germany E-mail: randerath@informatik.uni-koeln.de;Institut für Informatik, Universität zu Köln, 50969 Köln, Germany E-mail: esp@informatik.uni-koeln.de

  • Venue:
  • Annals of Mathematics and Artificial Intelligence
  • Year:
  • 2005

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Abstract

Let F=C1∧⋅⋅⋅∧Cm be a Boolean formula in conjunctive normal form over a set V of n propositional variables, s.t. each clause Ci contains at most three literals l over V. Solving the problem exact 3-satisfiability (X3SAT) for F means to decide whether there is a truth assignment setting exactly one literal in each clause of F to true (1). As is well known X3SAT is NP-complete [6]. By exploiting a perfect matching reduction we prove that X3SAT is deterministically decidable in time O(20.18674n). Thereby we improve a result in [2,3] stating X3SAT∈O(20.2072n) and a bound of O(20.200002n) for the corresponding enumeration problem #X3SAT stated in a preprint [1]. After that by a more involved deterministic case analysis we are able to show that X3SAT∈O(20.16254n).