“…where the solution is a set, or a sequence, or integers or other discrete objects [51]. The solution approaches to this sort of problems range from optimal mathematical models for benchmarking purposes to sub-optimal heuristic methods for [6,8,9,21,22,25,26,31,32,35,37,38,44,45] exact algorithms (B&B, DP) [9,17,18,21,27,34] constructive heuristics [6,9,31,[34][35][36]38] meta-heuristics [8, 21-23, 28, 29, 32, 33, 39-47] hybrid algorithms [8,9,25,26,32,33,40] simulation [16,25,30] scalability and fast response time. The common solution techniques together with the complete list of the related papers are summarized in Table 2.2(b) and described in the next few paragraphs.…”