Sorry, but the only ignorance here is your own. You assumed that "storing into an array" means that the array index is the only thing relevant for locating a re

Sorry, but the only ignorance here is your own. You assumed that "storing into an array" means that the array index is the only thing relevant for locating a record. But the fact that you're talking about inserts/deletes means that the array index of a particular element is mutable and therefore insufficient for uniquely locating a record. Which means you must perform some type of search to retrieve a particular item. Your O(1) getitem is nonsense. Yes, you can say "give me the 5th element of this array" but the discussion was about maps/dictionaries, where you're more often going to say "give me item foo that was inserted before". When folks like you post while obviously not paying attention, yes, you elicit a dismissive response.