A Primal Dual Algorithm for a Heterogeneous Traveling Salesman Problem
  Surveillance applications require a collection of heterogeneous vehicles to visit a set of targets. In this article, we consider a fundamental routing problem that arises in these applications involving two vehicles. Specifically, we consider a routing problem where there are two heterogeneous vehicles that start from distinct initial locations, and a set of targets. The objective is to find a tour for each vehicle such that each of the targets is visited at least once by a vehicle and the sum of the distances traveled by the vehicles is a minimum. We present a primal-dual algorithm for a variant of this routing problem that provides an approximation ratio of 2. 
Jungyun Bae and Sivakumar Rathinam
cs.DM cs.DS cs.RO math.CO