Compilare: user.cpp: In function ‘std::list<std::vector<int> > go(int&)’: user.cpp:13:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(rec.size() == n) ^ user.cpp:21:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < rec.size(); j++) { ^ user.cpp:22:55: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(rec[j] == i || rec.size() - j == abs(i - rec[j])) ^ user.cpp: In function ‘int main()’: user.cpp:50:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < r.begin()->size(); i++) { ^