Approximation of min-max and min-max regret versions of some combinatorial optimization problems

This paper investigates, for the first time in the literature, the approximation of minmax (regret) versions of classical problems like shortest path, minimum spanning tree, and knapsack. For a constant number of scenarios, we establish fully polynomial-time approximation schemes for the min-max versions of these problems, using relationships between multi-objective and min-max optimization. Using dynamic programming and classical trimming techniques, we construct a fully polynomial-time approximation scheme for min-max regret shortest path. We also establish a fully polynomial-time approximation scheme for min-max regret spanning tree and prove that min-max regret knapsack is not at all approximable. For a non constant number of scenarios, in which case minmax and min-max regret versions of polynomial-time solvable problems usually become strongly NP -hard, non-approximability results are provided for min-max (regret) versions of shortest path and spanning tree.