Is there any way to create a value sorted map?

Asked Mar 27 '18 at 11:36

Active Mar 27 '18 at 11:40

Viewed 76 times

I want to create map that instead sorting by default by key, its sorts by default by value. For example if I have the following map;

map<string, pair<int,int> > map;

I dont want to have it sorted by the key (string), I want it sorted by default by the first int in the pair (value).

edited Mar 27 '18 at 11:40

asked Mar 27 '18 at 11:36

Omair Iqbal

6

Why do you want to do that? (avoid XY problem) For enumeration, just sort the entries by value. – user202729 Mar 27 '18 at 11:38
4

Then, by definition, the value is not a value anymore. The "value" by definition becomes the key, and the "key" by definition becomes the value. – Mar 27 '18 at 11:39
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Maybe you are seeking for a [bimap](https://theboostcpplibraries.com/boost.bimap)? – Jodocus Mar 27 '18 at 11:41
Have you considered `std::map>` instead? – Dean Seo Mar 27 '18 at 11:43
You can provide a custom compare function to [std::map](http://en.cppreference.com/w/cpp/container/map) if you need to. – Jesper Juhl Mar 27 '18 at 11:47
Don't you want `std::map>` so ? – Jarod42 Mar 27 '18 at 12:00
Jesper Jhul, how do I write the compare function by value? – Omair Iqbal Mar 27 '18 at 12:02
@JesperJuhl Pretty sure after doing this the next question will be, "now how do i search by string?". I think the OP wants to iterate it by the value, but search it by string. – Fantastic Mr Fox Mar 27 '18 at 15:45
@Omair Iqbal "how do I write the compare function by value?" - you start by learning C++. Maybe pick up [a book](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) and by reading the documentation I already linked to. – Jesper Juhl Mar 27 '18 at 15:49
@Fantastic Mr Fox - possibly. We'll see. – Jesper Juhl Mar 27 '18 at 15:50

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