Brian, a very simple analysis would say something like, “If you think the middle element is likely to be an unusually bad pivot, exclude it as a possible pivot during random selection. If you have no such belief, why not go ahead and use them? If you do have such a belief, why let random selection occasionally select bad pivots?”
Brian, a very simple analysis would say something like, “If you think the middle element is likely to be an unusually bad pivot, exclude it as a possible pivot during random selection. If you have no such belief, why not go ahead and use them? If you do have such a belief, why let random selection occasionally select bad pivots?”