How to traverse a map by value

Question

Say there is a map: typedef map<int, string> MyMap;

I'd like to traverse it by the string, for example:

3 -> a
1 -> b
7 -> b
2 -> c

One way is to sort this map by its value. But I'm afraid this will have impact to find() efficiency (is it true?)

Another choice is to use boost::bimap. But, as you might notice, the value in MyMap is not unique, so bimap is not applicable here.

Is there a good way to do it?

score 2 · Accepted Answer · answered Dec 09 '11 at 15:47

2

I found a solution to use multiple values in boost.bimap: multiset_of

The data definition changed to:

#include <boost/bimap/multiset_of.hpp>
typedef boost::bimap<int, boost::bimaps::multiset_of<std::string> > MyMap;

Now I can traverse my data by either key or value.

answered Dec 09 '11 at 15:47

Deqing

If you don't want sorted traverse, you can make it unordered like `typedef boost::bimap, unordered_multiset_of > MyMap;` This will make the lookups much faster – balki Mar 28 '13 at 17:19

1 Answers1