Approximability of the subset sum reconfiguration problem

  • Authors:
  • Takehiro Ito;Erik D. Demaine

  • Affiliations:
  • Graduate School of Information Sciences, Tohoku University, Sendai, Japan;MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA

  • Venue:
  • TAMC'11 Proceedings of the 8th annual conference on Theory and applications of models of computation
  • Year:
  • 2011

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Abstract

The SUBSET SUM problem is a well-known NP-complete problem in which we wish to find a packing (subset) of items (integers) into a knapsack with capacity so that the sum of the integers in the packing is at most the capacity of the knapsack and at least a given integer threshold. In this paper, we study the problem of reconfiguring one packing into another packing by moving only one item at a time, while at all times maintaining the feasibility of packings. First we show that this decision problem is strongly NP-hard, and is PSPACE-complete if we are given a conflict graph for the set of items in which each vertex corresponds to an item and each edge represents a pair of items that are not allowed to be packed together into the knapsack. We then study an optimization version of the problem: we wish to maximize the minimum sum among all packings in the reconfiguration. We show that this maximization problem admits a polynomial-time approximation scheme (PTAS), while the problem is APX-hard if we are given a conflict graph.