An O(log n) approximation ratio for the asymmetric traveling salesman path problem

  • Authors:
  • Chandra Chekuri;Martin Pál

  • Affiliations:
  • Lucent Bell Labs, Murray Hill, NJ;Google Inc., New York, NY

  • Venue:
  • APPROX'06/RANDOM'06 Proceedings of the 9th international conference on Approximation Algorithms for Combinatorial Optimization Problems, and 10th international conference on Randomization and Computation
  • Year:
  • 2006

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Abstract

Given an arc-weighted directed graph G = (V,A,ℓ) and a pair of vertices s,t, we seek to find an s-twalk of minimum length that visits all the vertices in V. If ℓ satisfies the asymmetric triangle inequality, the problem is equivalent to that of finding an s-tpath of minimum length that visits all the vertices. We refer to this problem as ATSPP. When s = t this is the well known asymmetric traveling salesman tour problem (ATSP). Although an O(logn) approximation ratio has long been known for ATSP, the best known ratio for ATSPP is $O(\sqrt{n})$. In this paper we present a polynomial time algorithm for ATSPP that has approximation ratio of O(logn). The algorithm generalizes to the problem of finding a minimum length path or cycle that is required to visit a subset of vertices in a given order.