Compilare: user.cpp: In function ‘int main()’: user.cpp:30:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<v.size();i++) ^ user.cpp:33:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while ((j+1<v.size()) && (v[j+1].first==v[i].first)) ^ user.cpp:42:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<w.size();i++) ^