Shift-and-merge technique for the DP solution of the time-constrained backpacker problem

  • Authors:
  • Byungjun You;Takeo Yamada

  • Affiliations:
  • Department of Computer Science, The National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan;Department of Computer Science, The National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan

  • Venue:
  • Computers and Operations Research
  • Year:
  • 2012

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Abstract

We formulate the time-constrained backpacker problem as an extension of the classical knapsack problem (KP), where a 'backpacker' travels from a origin to a destination on a directed acyclic graph, and collects items en route within the capacity of his knapsack and within a fixed time limit. We present a dynamic programming (DP) algorithm to solve this problem to optimality, and a 'shift-and-merge' DP algorithm to solve larger instances. The latter is an extension of the list-type DP, which has been successful for one-dimensional KPs, to the two-dimensional case. Computational experiments on a series of instances demonstrate advantage of the shift-and-merge technique over commercial MIP solvers.