Elegant way to test if members of array A are present in array B?

[Paul Backus]

On Wednesday, 12 June 2019 at 06:57:55 UTC, Robert M. Münch wrote:
>> If you use an associative array or a set, it's O(n) time and 
>> O(n) space.
>
> I don't see how this is the case. The AA itself has some 
> overhead too. So, the checking loop is O(n) but the AA lookups 
> not.

Hash table insertion and lookup lookup both have amortized O(1) 
complexity, and D's associative arrays are implemented using hash 
tables.