Podam pełny komunikat:
/usr/include/c++/7/bits/predefined_ops.h: In instantiation of ‘bool __gnu_cxx::__ops::_Iter_less_iter::operator()(_Iterator1, _Iterator2) const [with _Iterator1 = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >; _Iterator2 = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >]’:
/usr/include/c++/7/bits/stl_algo.h:4880:14: required from ‘_OutputIterator std::__merge(_InputIterator1, _InputIterator1, _InputIterator2, _InputIterator2, _OutputIterator, _Compare) [with _InputIterator1 = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >; _InputIterator2 = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >; _OutputIterator = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’
/usr/include/c++/7/bits/stl_algo.h:4937:37: required from ‘_OIter std::merge(_IIter1, _IIter1, _IIter2, _IIter2, _OIter) [with _IIter1 = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >; _IIter2 = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >; _OIter = __gnu_cxx::__normal_iterator<Edge*, std::vector<Edge> >]’
main.cpp:266:99: required from here
/usr/include/c++/7/bits/predefined_ops.h:43:23: error: no match for ‘operator<’ (operand types are ‘Edge’ and ‘Edge’)
{ return *__it1 < *__it2; }
~~~~~~~^~~~~~~~