Compilare: user.cpp: In function ‘std::string Normalize(std::string)’: user.cpp:24:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<str.size();++i) ^ user.cpp:26:25: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(buffer[str[i]]==0) ^ user.cpp:28:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] buffer[str[i]]='a'+index; ^ user.cpp:31:29: warning: array subscript has type ‘char’ [-Wchar-subscripts] str[i]=buffer[str[i]]; ^