Preferred data structure if you have two keys and can not use boost?

Question

What data structure do you prefer if you have two keys, and can not use boost::multiindex?

I can have multiple records with Key1 and/or Key2 but there will be only one record for the combination of KEY1 KEY2. My requirements are that I should be able to search

All the records for KEY1
All the records for KEY2
Single record given KEY1 and KEY2

Currently I am using std::map

std::map <CString, std::vector<CutomClass>> m_map;

the So first key is used in map and another is part of my class (this class has more data alone with second key)

Is there any other data structure I can use instead?

I cant use boost library for some reason so I am looking for suggestion only from standard library.

SergeyA · Accepted Answer · 2018-02-23T18:09:18.933

1

The way I would implement this would be with three data structures. Two multi_map (or unordered_multimap), one keyed off KEY1, and another keyed of KEY2.

The third would me map (unordered_map) of KEY1 + KEY2 combination. For map, that would be simple and straightforward, for unordered_map, you'd have to combine the key, or, hash two subkeys and than combine the hash.

And I seem to forget to mention, only one of those maps (keyed of combined key) will hold actual values, two other maps will hold pointers to the values held in combined map.

edited Feb 23 '18 at 18:09

answered Feb 23 '18 at 16:08

SergeyA

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This is a wonderful suggestion but These data are huge. I cant have multiple copies. – Geek Feb 23 '18 at 16:50
If you're not willing to have redundant data, you're going to pay for it in lookup times when you want to lookup by one key or the other. – Silvio Mayolo Feb 23 '18 at 17:08
@Geek, did I forget to mention that two of those maps hold pointers? – SergeyA Feb 23 '18 at 18:08

Preferred data structure if you have two keys and can not use boost?

1 Answers1