Compilare: user.cpp: In function ‘int main()’: user.cpp:30:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < sol.size(); ++ i) ^ user.cpp:31:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] cout << sol[i] << " \n"[i + 1 == sol.size()]; ^