Iterate/sort associative array by value?

[Cym13]

On Sunday, 7 April 2019 at 15:41:51 UTC, Robert M. Münch wrote:
> I have an AA int[ulong] and would like to traverse the AA from 
> biggest to smallest by value. Is there an elegant way to do 
> this?
>
> The only way I can imagine is to create an "reverse" AA of the 
> form ulong[int] and than sort by keys. Traverse this AA and use 
> the value as the lookup key in the orginial array. But this 
> feels all a bit wired...

You could use sort to gather the indexes in order then traverse 
from there:

     aa.byKey.array.sort!((a, b) => aa[a]<aa[b])

With a wrapper caching that order and making it transparent as 
well as update on insertion (which should be in log(n) since you 
know have an ordered list of indexes, you can use dichotomy to 
update the indexes without walking all your AA again) I think you 
could have a nice little container.

However if double entry is necessary maybe a simpler 2D array 
would be easier to work with?