Compilare: user.cpp: In function ‘int compare(std::string, std::string)’: user.cpp:10:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s1.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:34:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size() - 1;i++) ^