Semi-preemptive routing on trees

We study a variant of the pickup-and-delivery problem (PDP) in which the objects that have to be transported can be reloaded at most d times, for a given d N. This problem is known to be polynomially solvable on paths or cycles and NP-complete on trees. We present a (4/3 + )-approximation algorithm if the underlying graph is a tree. By using a result of Charikar et al. (1998), this can be extended to a O(log n log log n)-approximation for general graphs. Key words: pickup and delivery, dial-a-ride, transportation, approximation, colored arborescences, stacker crane

• Type: Journal
• Year: 2008
• Where: DAM
• Authors: Sven Oliver Krumke, Dirk Räbiger, Rainer Schrader
• Keywords: Charikar Et, DAM 2008, NP-complete, Pickup-and-delivery Problem