Compilare: user.cpp: In function ‘int main()’: user.cpp:23:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<r.size(); ++i) ^ user.cpp:25:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<v[r[i]].size();++j) ^ user.cpp:32:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<r.size(); ++i) ^