Approximating a vehicle scheduling problem with time windows and handling times

  • Authors:
  • Hiroshi Nagamochi;Takaharu Ohnishi

  • Affiliations:
  • Department of Applied Mathematics and Physics, Kyoto University, Yoshida Honmachi, Sakyo, Kyoto 606-8501, Japan;Sumitomo Electric Industries, Ltd., Japan

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2008

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Abstract

In this paper, we study a problem of finding a vehicle scheduling to process a set of n jobs which are located in an asymmetric metric space. Each job j has a positive handling time h(j), a time window [r(j),d(j)], and a benefit b(j). We consider the following two problems: MAX-VSP asks to find a schedule for a single vehicle to process a subset of jobs with the maximum benefit; and MIN-VSP asks to find a schedule to process all given jobs with the minimum number of vehicles. We first give an O(@rn^3^+^@c) time algorithm that delivers a 2-approximate solution to MAX-VSP, where @r=max"j","j"^"'(d(j)-r(j))/h(j^') and @c is the maximum number of jobs that can be processed by the vehicle after processing a job j and before visiting the processed job j again by deadline d(j). We then present an O(@rn^4^+^@c) time algorithm that delivers a 2H(n)-approximate solution to MIN-VSP, where H(n) is the nth harmonic number.