Eroare de compilare: In file included from /usr/include/c++/4.8/algorithm:62:0, from user.cpp:2: /usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_RandomAccessIterator std::__unguarded_partition(_RandomAccessIterator, _RandomAccessIterator, const _Tp&) [with _RandomAccessIterator = a*; _Tp = a]’: /usr/include/c++/4.8/bits/stl_algo.h:2307:70: required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = a*]’ /usr/include/c++/4.8/bits/stl_algo.h:2338:54: required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = a*; _Size = int]’ /usr/include/c++/4.8/bits/stl_algo.h:5475:36: required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = a*]’ user.cpp:102:15: required from here /usr/include/c++/4.8/bits/stl_algo.h:2266:20: error: no match for ‘operator<’ (operand types are ‘a’ and ‘const a’) while (*__first < __pivot) ^ /usr/include/c++/4.8/bits/stl_algo.h:2266:20: note: candidates are: user.cpp:7:7: note: bool a::operator<(a&) bool operator<(a & x) { ^ user.cpp:7:7: note: no known conversion for argument 1 from ‘const a’ to ‘a&’ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:64:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_pair.h:220:5: note: template<class _T1, class _T2> constexpr bool std::operator<(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&) operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) ^ /usr/include/c++/4.8/bits/stl_pair.h:220:5: note: template argument deduction/substitution failed: In file included from /usr/include/c++/4.8/algorithm:62:0, from user.cpp:2: /usr/include/c++/4.8/bits/stl_algo.h:2266:20: note: ‘a’ is not derived from ‘const std::pair<_T1, _T2>’ while (*__first < __pivot) ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_iterator.h:297:5: note: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&) operator<(const reverse_iterator<_Iterator>& __x, ^ /usr/include/c++/4.8/bits/stl_iterator.h:297:5: note: template argument deduction/substitution failed: In file included from /usr/include/c++/4.8/algorithm:62:0, from user.cpp:2: /usr/include/c++/4.8/bits/stl_algo.h:2266:20: note: ‘a’ is not derived from ‘const std::reverse_iterator<_Iterator>’ while (*__first < __pivot) ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38,