Compilare: user.cpp: In function ‘int getkey(std::string)’: user.cpp:27:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < x.size(); ++i) ^ user.cpp: In function ‘int add(std::string)’: user.cpp:36:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < h[key].size(); ++i) ^