Compilare: user.cpp: In function ‘void build(int)’: user.cpp:55:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (lg[index] < L[index].size()) lg[index] *= 2; ~~~~~~~~~~^~~~~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:114:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<L.size();i++){ ~^~~~~~~~~