Compilare: user.cpp: In function ‘int cheie(std::string&)’: user.cpp:17:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < str.size (); ++i) ^ user.cpp:20:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < str.size (); ++i) ^ user.cpp:25:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i; j < str.size (); ++j) ^ user.cpp:32:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < str.size (); ++i, p10 *= 10) ^