Compilare: user.cpp: In function ‘int process(int)’: user.cpp:22:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (idx < s.size() && (s[ idx ] < 'a' || s[ idx ] > 'z')) ^ user.cpp:24:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (idx == s.size()) ^ user.cpp:26:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (idx < s.size() && s[ idx ] >= 'a' && s[ idx ] <= 'z') ^ user.cpp: In function ‘int main()’: user.cpp:57:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (idx < s.size()) ^