Custom sorting in ordered container

Question

I've got an ordered container (usually std::vector) with objects, say

Banana
Apple
Peach

and above custom order. Now the objects go through some processing, might have been removed from the container and reinserted, resulting in a new ordered container.

I have stored the order (Banana -> 1, Apple -> 2, Peach -> 3) separately and would like to re-establish that particular custom order in the new ordered container.

The objects are already present at this time (i.e. I cannot simply insert in the desired order).

So rather than swapping excessively with some naive algorithm on my own I was wondering if there's some algorithm in the standard library I could employ in a cunning way..?

Why not leave the objects in the container and copy out of the container? vector returns a reference that you can work on. — NathanOliver
– NathanOliver, Commented Jan 12, 2015 at 15:11
Are you looking for something like std::sort(fruits.begin(), fruits.end(), [](const std::string& a, const std::string& b) { return rank[a] < rank[b]; }); where rank is std::map<std::string, int> holding your string-to-rank mapping? — Igor Tandetnik
– Igor Tandetnik, Commented Jan 12, 2015 at 15:19
@IgorTandetnik Cheers - that did the job.. could have thought of that myself.. — cacau
– cacau, Commented Jan 13, 2015 at 6:50

chris · Accepted Answer · 2015-01-12 15:27:14Z

std::sort is in the standard library AND it's pretty cunning! It can sort by the default < operator (which you could override for your fruit) or you can supply a comparator that's external to your class' implementation.

http://www.cplusplus.com/reference/algorithm/sort/?kw=sort

cacau · Accepted Answer · 2015-01-13 06:50:00Z

Well, pretty much what Igor wrote does the job..

std::sort(fruits.begin(), fruits.end(), [&](const std::string& a, const std::string& b) { return rank[a] < rank[b]; } );

where rank is std::map<std::string, int> holding the string-to-rank mapping

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