For #1, it really depends on what you mean by "array" and what you need to use it for. Sounds like an XY problem. If you take it to mean a more abstract concep

For #1, it really depends on what you mean by "array" and what you need to use it for. Sounds like an XY problem. If you take it to mean a more abstract concept of a list of things that can be iterated and accessed by index, then the fastest implementation is O(1): build no data structure at all - just implement the iterator and index functions. If you take it to mean physically manipulating atoms on a chip to be in a certain state, then you'll actually have to do something :)