Polynomial Time Approximation Schemes for the Median Tour Problem
and the Newspaper Delivery Problem in the Euclidean Plane
Abstract:
An instance of the Median Tour Problem (also referred to as the
Traveling Circus Problem) is defined by a set P={v1,
... ,v} of points in the plane and a partition
P1, ... ,Pk of P. The objective is to minimize
the length of the Hamiltonian tour through facilities vij
in Pj, plus the sum of radial distances from the remaining sites to
their closest facility. The points may be thought of as villages. Over
a given period, a circus will tour some of the villages, while people
from the remaining villages will travel to the circus. For the
euclidean version of this problem we give an PTAS, i.e. an
1+2SQRT(2)/m-approximation algorithm whose running time is polinomial
in n for every fixed integer m. The PTAS is
constructed using Mitchells m-Guillotine Subdivisions.
Given a set P={v1, ... ,v} of points in the
plane and an integer 1≤k≤n, in the Newspaper Delivery
Problem one is to design a primary tour through a subset of
k points of P and secondary tours linking the
remaining sites to the primary tour. The total length of all tours is
to be minimized. The primary tour may correspond to a newspaper
delivery route comprising the printing plant and a number of transfer
points. These transfer points are used as anchor points for secondary
delivery routes. We describe an 1+1/c-approximarion algorithm for the
Euclidean version of this problem which is a PTAS when k=O(n). The
construction of the PTAS is dased on an extension of Aroras PTAS for
Euclidean TSP.