An o *(1.84 k) parameterized algorithm for the multiterminal cut problem

  • Authors:
  • Yixin Cao;Jianer Chen;Jia-Hao Fan

  • Affiliations:
  • Inst. for Computer Science and Control, Hungarian Academy of Sciences, Hungary;School of Information Science & Engineering, Central South University, P.R. China,Department of Computer Science and Engineering, Texas A&M University;Department of Computer Science and Engineering, Texas A&M University

  • Venue:
  • FCT'13 Proceedings of the 19th international conference on Fundamentals of Computation Theory
  • Year:
  • 2013

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Abstract

We study the multiterminal cut problem, which, given an n-vertex graph whose edges are integer-weighted and a set of terminals, asks for a partition of the vertex set such that each terminal is in a distinct part, and the total weight of crossing edges is at most k. Our weapons shall be two classical results known for decades. One is max volume min (s,t)-cuts by [Ford and Fulkerson, Flows in Networks. Princeton University Press, 1962], and the other is isolating cuts by [Dahlhaus et al., The complexity of multiterminal cuts. SIAM J. Comp. 23(4), 1994]. We sharpen these old weapons with the help of submodular functions, and apply them to this problem, which enable us to design a more elaborated branching scheme on deciding whether a non-terminal vertex is with a terminal or not. This bounded search tree algorithm can be shown to run in $1.84^k\cdot n^{{\cal O}(1)}$, thereby breaking the $2^k\cdot n^{{\cal O}(1)}$ barrier. As a by-product, it gives a $1.36^k\cdot n^{{\cal O}(1)}$ algorithm for 3-terminal cut. The preprocessing applied on non-terminal vertices might be of use for study of this problem from other aspects.