Donation Center Location Problem

Abstract

We introduce and study the {\em donation center location} problem, which
has an additional application in network
testing and may also be of independent interest as a general graph-theoreticproblem.Given a set of agents and a set of centers, where agents have preferences over centers and centers have capacities, 
 the goal is to open a subset of centers and to assign a maximum-sized subset of agents to their most-preferred 
 open centers, while respecting the capacity constraints.

We prove that in general, the problem
is hard to approximate within $n^{1/2-\epsilon}$ for any $\epsilon>0$.
In view of this, we investigate two special cases.
In one, every agent has a bounded number of centers on her preference list,
and in the other, all preferences are induced by a line-metric.
We present constant-factor approximation algorithms
for the former and exact polynomial-time algorithms for the latter.
Of particular interest among our techniques are an analysis of the greedy
algorithm for a variant of the maximum coverage problem called\emph{frugal coverage}, the use of maximum matching subroutine with subsequent
modification, analyzed using a counting argument, and a reduction to the independent set problem  
on \emph{terminal intersection graphs}, which we show to be
a subclass of trapezoid graphs.