Compilare: user.cpp: In function ‘bool bkt(const std::vector<int>&)’: user.cpp:20:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v.size(); ++i) ~~^~~~~~~~~~ user.cpp:21:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i + 1; j < v.size(); ++j) { ~~^~~~~~~~~~ user.cpp:25:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 0; k < v.size(); ++k) if(k != i && k != j) ret.push_back(v[k]); ~~^~~~~~~~~~