sort vectors in map

HOW to sort vectors inside a map based on the size of th开发者_Go百科e vectors?

example:

map<int, vector<int> > 

sort based on the size of the vector in order to remove some elements later within the less size.

1,2,3,4

2,5

6,7,8

after sort and delete ...

1,2,3,4

6,7,8

5

I hope this clarify the intended need.

Thanks

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A map is an ordered container on which the order predicate applies to the key.

For example you can have a std::map<int, std::vector<int>, std::less<int> >

Here your key is not the vector, hence you cannot do what you are looking for with your map.

Here maybe you want a std::map<std::vector<int>, int, some_struct> where some_struct is a functor that defines a strict order relationship on your vectors.

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You can do it provided the size of the vector doesn't change:

map <int, vector<int> > amap;
vector <int> v;
v.push_back( 42 );
amap.insert( make_pair( v.size(), v ));

If the size of the vector does change, you would have to remove the old entry and re-insert.