Compilare: user.cpp: In function ‘void inserare(nod*, std::string)’: user.cpp:21:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<s.length(); ++i){ ^ user.cpp: In function ‘void stergere(nod*, std::string)’: user.cpp:37:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.length(); ++i){ ^ user.cpp: In function ‘void aparitii(nod*, std::string)’: user.cpp:45:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.length(); ++i){ ^ user.cpp: In function ‘void prefix(nod*, std::string)’: user.cpp:51:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.length(); ++i){ ^