Finding the index of the maximum value in an associative array

[cym13 via Digitalmars-d-learn]

On Tuesday, 30 May 2017 at 17:57:04 UTC, Lyle wrote:
> Hi,
>
> I have an associative array of type int[ulong] and I'm trying 
> to get the index of the maximum value, like this:
>
> int[ulong] aa = [1UL: 2000,
>                  2UL: 5000,
>                  5UL: 1000];
>
> writeln(aa.maxIndex); // should print 2
>
> Can anyone help me out?
>
> Many thanks,
> Lyle

Simple enough: get all key/values pairs in the AA, and ask for 
the element which is the maximum relatively to the value, then 
take its key.

     auto maxIndex(int[ulong] aa) {
         import std.algorithm;

         return aa.byKeyValue
                  .maxElement!(x => x.value)
                  .key;
     }