Finding small balanced separators

  • Authors:
  • Uriel Feige;Mohammad Mahdian

  • Affiliations:
  • Microsoft Research, Redmond, WA;Microsoft Research, Redmond, WA

  • Venue:
  • Proceedings of the thirty-eighth annual ACM symposium on Theory of computing
  • Year:
  • 2006

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Abstract

Let G be an n-vertex graph that has a vertex separator of size k that partitions the graph into connected components of size smaller than α n, for some fixed 2/3 ≤ α unless the graph contains an (α+ε)-separator of size strictly less than k, in which case our algorithm finds one such separator. For fixed ε, the running time of our algorithm is nO(1)2O(k), which is polynomial for k = O(log n). For bounded degree graphs (as well as for the case of finding balanced edge separators), we present a deterministic algorithm with similar running time.Our algorithm involves (among other things) a new concept that we call (ε,k)-samples. This is related to the notion of detection sets for network failures, introduced by Kleinberg [FOCS 2000]. Our proofs adapt and simplify techniques that were introduced by Kleinberg. As a by-product, our proof improves the known bounds on the size of detection sets. We also show applications of (ε,k)-samples to problems in approximation algorithms and rigorous analysis of heuristics.