Eroare de compilare: user.cpp: In function ‘void dfs(std::vector<std::vector<int> >&, std::vector<int>&, std::stack<int>&, int)’: user.cpp:10:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<v[i].size();j++) ~^~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:34:5: error: no match for ‘operator<<’ (operand types are ‘std::ifstream {aka std::basic_ifstream<char>}’ and ‘__gnu_cxx::__alloc_traits<std::allocator<int> >::value_type {aka int}’) f << s.top()<<" "; ~~^~~~~~~~~~ user.cpp:34:5: note: candidate: operator<<(int, __gnu_cxx::__alloc_traits<std::allocator<int> >::value_type {aka int}) <built-in> user.cpp:34:5: note: no known conversion for argument 1 from ‘std::ifstream {aka std::basic_ifstream<char>}’ to ‘int’ In file included from /usr/include/c++/6/string:52:0, from /usr/include/c++/6/bits/locale_classes.h:40, from /usr/include/c++/6/bits/ios_base.h:41, from /usr/include/c++/6/ios:42, from /usr/include/c++/6/ostream:38, from /usr/include/c++/6/iostream:39, from user.cpp:1: /usr/include/c++/6/bits/basic_string.h:5340:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) operator<<(basic_ostream<_CharT, _Traits>& __os, ^~~~~~~~ /usr/include/c++/6/bits/basic_string.h:5340:5: note: template argument deduction/substitution failed: user.cpp:34:14: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’ f << s.top()<<" "; ^ In file included from /usr/include/c++/6/bits/ios_base.h:46:0, from /usr/include/c++/6/ios:42, from /usr/include/c++/6/ostream:38, from /usr/include/c++/6/iostream:39, from user.cpp:1: /usr/include/c++/6/system_error:209:5: note: candidate: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::error_code&) operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e) ^~~~~~~~ /usr/include/c++/6/system_error:209:5: note: template argument deduction/substitution failed: user.cpp:34:14: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’ f << s.top()<<" "; ^ In file included from /usr/include/c++/6/iostream:39:0, from user.cpp:1: /usr/include/c++/6/ostream:497:5: note: candidate: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT) operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c) ^~~~~~~~ /usr/include/c++/6/ostream:497:5: note: template argument deduction/substitution failed: user.cpp:34:14: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’ f << s.top()<<" "; ^ In file included from /usr/include/c++/6/iostream:39:0, from user.cpp:1: /usr/include/c++/6/ostream:502:5: note: candidate: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char) operator<<(basic_ostream<_CharT, _Traits>& __out, char __c) ^~~~~~~~