Compilare: main.cpp: In function 'std::vector<std::complex<double> > multiply(const std::vector<std::complex<double> >&, const std::vector<std::complex<double> >&)': main.cpp:80:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(n<(a.size()+b.size()) ){ ~^~~~~~~~~~~~~~~~~~~~ main.cpp: In function 'int32_t main()': main.cpp:210:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.length(); i++){ ~^~~~~~~~~~~ main.cpp:237:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<p[i].size(); j++){ ~^~~~~~~~~~~~ main.cpp:243:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=((int)s.length() )-1; i<(t.length()); i++ ){ ~^~~~~~~~~~~~~