Compilare: main.cpp: In function 'void fft(std::vector<Complex>&, int)': main.cpp:68:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pol.size(); ++i) ~~^~~~~~~~~~~~ main.cpp:72:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int len = 1; len < pol.size(); len*= 2) { ~~~~^~~~~~~~~~~~ main.cpp:75:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int pos = 0; pos < pol.size(); pos+= len * 2) { ~~~~^~~~~~~~~~~~ main.cpp:86:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pol.size(); ++i) ~~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:104:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (v1.size() <= t) ~~~~~~~~~~^~~~ main.cpp:110:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (v2.size() <= t) ~~~~~~~~~~^~~~ main.cpp:116:32: warning: suggest parentheses around '-' in operand of '&' [-Wparentheses] while (v1.size() & v1.size() - 1) ~~~~~~~~~~^~~ main.cpp:122:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v1.size(); ++i) ~~^~~~~~~~~~~ main.cpp:126:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v1.size(); ++i) ~~^~~~~~~~~~~