iterating over c++ map<int, list<int>>

Question

I am getting this error while trying to iterate over a map and its list member:

error: 'template<class _Category, class _Tp, class _Distance, class _Pointer, class _Reference> struct std::iterator' used without template parameters invalid use of qualified-name '<declaration error>::ii' error: 'ii' was not declared in this scope error: 'struct std::_Rb_tree_iterator<std::pair<const int, std::list<int, std::allocator<int> > > >' has no member named 'second' error: 'struct std::_Rb_tree_iterator<std::pair<const int, std::list<int, std::allocator<int> > > >' has no member named 'second'

This is the code (the map is correctly populated before):

map<int, list<int> >::iterator it; list<int>iterator:: ii; for(it=this->mapName.begin(); it!=this->mapName.end(); ++it){ cout<<(*it).first<<" { "; for(ii = (*it).second().begin(); ii!=(*it).second.end(); ++ii){ cout<<(*ii)<<" "; } cout << " }" << endl; }

Any advices?

Shouldn't this line list<int>iterator:: ii; be list<int>::iterator ii;? — Hindol
– Hindol, Commented May 23, 2012 at 12:56

Luchian Grigore · Accepted Answer · 2012-05-23 12:56:01Z

You have a syntax error here:

 list<int>iterator::

should be

 list<int>::iterator

Also,

(*it).second().begin()

should be

(*it).second.begin()

Happy Green Kid Naps · Accepted Answer · 2012-05-23 13:41:15Z

You could do away with the inner for loop with -

 std::copy( it->second.begin(), it->second.end(), std::ostream_iterator<int>(std::cout, " ") );

Which also means that you could get rid off the declaration of ii.

kleopatra · Accepted Answer · 2013-11-25 11:12:43Z

map<int, list<int> >::iterator it; list<int>::iterator ii; for(it=this->mapName.begin(); it!=this->mapName.end(); ++it){ cout<<(*it).first<<" { "; for(ii = (*it).second.begin(); ii!=(*it).second.end(); ++ii){ cout<<(*ii)<<" "; } cout << " }" << endl; }

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