Eroare de compilare: In file included from /usr/include/c++/4.8/algorithm:62:0, from user.cpp:3: /usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<elem*, std::vector<elem> >; _Tp = elem]’: /usr/include/c++/4.8/bits/stl_algo.h:2307:70: required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<elem*, std::vector<elem> >]’ /usr/include/c++/4.8/bits/stl_algo.h:2338:54: required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<elem*, std::vector<elem> >; _Size = int]’ /usr/include/c++/4.8/bits/stl_algo.h:5475:36: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<elem*, std::vector<elem> >]’ user.cpp:72:26: required from here /usr/include/c++/4.8/bits/stl_algo.h:2269:19: error: passing ‘const elem’ as ‘this’ argument of ‘bool elem::operator<(const elem&)’ discards qualifiers [-fpermissive] while (__pivot < *__last) ^