On Sat, 28 Jan 2012 06:36:49 +1100, Andrei Alexandrescu
<[email protected]> wrote:
Here's a multikey sorting problem that's bothering me; I think it's well
researched but I can't find the right keywords.
Say we have a collection of people with height and hair length
information. We want to get people who are "tall and long-haired". More
precisely, we want to order people by rank(p.height) +
rank(p.hairlength), where rank(p.k) is the function that returns the
rank of person p if ordered by key k.
The brute force approach would essentially compute the two ranks and
then sort by their sum. That's three sorts and at least one temporary
array. But I think things can be done considerably better. Any ideas?
Just a further clarification ...
If a person is tall and has short hair, would they be included in the
sort? In other words, are you ONLY looking for tall AND long-haired people
or are you looking for relative ranking of tallness and hairiness?
--
Derek Parnell
Melbourne, Australia
