C++: Storing groups of three in a multimap

Question

I was wondering how you implement a multimap with groups of three values. For instance: [{a,b,c}, {d,e,f}]

Do you have to use std::pair?

What sort of thing would be the lookup key? Does your C++ support tuples? — EvilTeach, Oct 19 '13 at 17:10
Using the example I wrote above, a and d would be the lookup keys. — Julia, Oct 19 '13 at 17:12

score 3 · Accepted Answer · answered Oct 19 '13 at 17:15

3

Yes. Using std::pair is a reasonable way to represent the values {b,c} and {e,f} You would store each one in the multimap with key a, value {b,c} and key D, value {e,f}.

Then later you might have key a, value {z,y}. When that is inserted, you can then find key a, and it will return a iterator that you can fetch all of the values associated with key a.

If you do have tuples, then you might consider using key a, with the tuple {a,b,c}.

answered Oct 19 '13 at 17:15

EvilTeach

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There are many examples on this site and elsewhere. Consider http://stackoverflow.com/questions/247818/stlmultimap-how-do-i-get-groups-of-data?rq=1 Look to the right on this page, under the Related stuff. There are lots of good links that show you things about multimaps – EvilTeach Oct 19 '13 at 17:20

score 1 · Answer 2 · answered Oct 19 '13 at 17:23

1

If you mean the key that represents itself a group of three values then for example you can use std::array as the key.

For example

std::multimap<std::array<int, 3>, std::string> m;

answered Oct 19 '13 at 17:23

Vlad from Moscow

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C++: Storing groups of three in a multimap

2 Answers2