Approximation Algorithms for the Generalized Multiple Knapsack Problems with k Restricted Elements

We are given a set of items, and a set of knapsacks. Both the weight and the profit of an item are functions of the knapsack, and each knapsack has a positive real capacity. A restriction is setting that the number of the items which are admissible to each knapsack is no more than k, and these items are taken as input for each knapsack. We consider two following objectives: (1) maximizing the total profit of all the knapsacks (Max-Sum k-GMK); (2) maximizing the minimum profit of all the knapsacks (Max-Min k-GMK). We show that the two problems are NP-complete when k is greater than or equal t to 4. For the Max-Sum k-GMK problem, we can obtain a 1/2-approximation algorithm, and especially when k=2, we design an optimal algorithm. For the Max-Min k-GMK problem, we present a 1/(k-1)-approximation algorithm, and especially when k=2, this algorithm is an optimal algorithm.