Compilare: user.cpp: In function ‘bool func(std::__cxx11::string, std::__cxx11::string)’: user.cpp:13:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size();i++) ^ user.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else for(int i=0;i<b.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:32:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ^