1. We need to iterate through the index in order 2. We need to look up in the index at random 3. We need to append to the index 4. We need to build the index EITHER in order or out of order, depending on algorithm It's rule 4 that got us this time. The best algorithm for performing an intersection on an array in-order the result out-of-order. The best algorithm for building an intersection in-order searches the array out-of-order. #notetaking #database