Compilare: user.cpp: In function ‘void adauga(std::string)’: user.cpp:25:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0; i<s.size(); i++) ^ user.cpp: In function ‘void sterge(std::string)’: user.cpp:41:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0; i<s.size(); i++) ^ user.cpp: In function ‘int nr_aparitii(std::string)’: user.cpp:58:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0; i<s.size(); i++) ^ user.cpp: In function ‘int prefix(std::string)’: user.cpp:72:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0; i<s.size(); i++) ^