Compilare: user.cpp: In function ‘int main()’: user.cpp:46:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) ^ user.cpp:58:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) ^ user.cpp:68:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = int(a.size()); i < b.size(); i++) ^