A Unified PTAS for Prize Collecting TSP and Steiner Tree Problem in Doubling Metrics

Authors T-H. Hubert Chan, Haotian Jiang, Shaofeng H.-C. Jiang

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Author Details

T-H. Hubert Chan
  • Department of Computer Science, The University of Hong Kong, Hong Kong, China
Haotian Jiang
  • Department of Physics, Tsinghua University, Beijing, China
Shaofeng H.-C. Jiang
  • The Weizmann Institute of Science, Rehovot, Israel

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T-H. Hubert Chan, Haotian Jiang, and Shaofeng H.-C. Jiang. A Unified PTAS for Prize Collecting TSP and Steiner Tree Problem in Doubling Metrics. In 26th Annual European Symposium on Algorithms (ESA 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 112, pp. 15:1-15:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)


We present a unified (randomized) polynomial-time approximation scheme (PTAS) for the prize collecting traveling salesman problem (PCTSP) and the prize collecting Steiner tree problem (PCSTP) in doubling metrics. Given a metric space and a penalty function on a subset of points known as terminals, a solution is a subgraph on points in the metric space, whose cost is the weight of its edges plus the penalty due to terminals not covered by the subgraph. Under our unified framework, the solution subgraph needs to be Eulerian for PCTSP, while it needs to be a tree for PCSTP. Before our work, even a QPTAS for the problems in doubling metrics is not known. Our unified PTAS is based on the previous dynamic programming frameworks proposed in [Talwar STOC 2004] and [Bartal, Gottlieb, Krauthgamer STOC 2012]. However, since it is unknown which part of the optimal cost is due to edge lengths and which part is due to penalties of uncovered terminals, we need to develop new techniques to apply previous divide-and-conquer strategies and sparse instance decompositions.

Subject Classification

ACM Subject Classification
  • Theory of computation → Routing and network design problems
  • Doubling Dimension
  • Traveling Salesman Problem
  • Polynomial Time Approximation Scheme
  • Steiner Tree Problem
  • Prize Collecting


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