Compilare: user.cpp: In function ‘void fft(std::vector<int>&, std::vector<int>&)’: user.cpp:58:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < pol1.size(); i ++ ) ^ user.cpp:59:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < pol2.size(); j ++ ) ^ user.cpp:67:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( sz < pol1.size() + pol2.size() ) ^ user.cpp:71:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < pol1.size(); i ++ ) ^ user.cpp:75:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < pol2.size(); i ++ ) ^ user.cpp: In function ‘int main()’: user.cpp:97:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < arr.size(); i ++ ) ^ user.cpp:101:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < arr.size(); i ++ ) ^ user.cpp:118:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( x >= pol.size() ) ^