topN using a heap

[Andrei Alexandrescu via Digitalmars-d]

On 1/17/16 8:07 PM, deadalnix wrote:
> A common way to do it is to go quicksort, but only recurse on one side
> of the set. That should give log(n)^2 complexity on average.

Yah, that's quickselect (which this work started from). It's linear, and 
you can't get top n in sublinear time because you need to look at all 
elements. -- Andrei