Robust recoverable recoverable and two-stage selection problems

In this paper the following selection problem is discussed. A set of n items is given and we wish to choose a subset of exactly p items of the minimum total cost. This problem is a special case of 0-1 knapsack in which all the item weights are equal to 1. Its deterministic version has an O(n)-time algorithm, which consists in choosing p items of the smallest costs. In this paper it is assumed that the item costs are uncertain. Two robust models, namely two-stage and recoverable ones, under discrete and interval uncertainty representations, are discussed. Several positive and negative complexity results for both of them are provided. (C) 2017 Elsevier B.V. All rights reserved.