Method differentiate

Math/Subset Sum Problem.cpp:200–204

    return vector<mint>(a.begin() + l, a.begin() + r);
  }
  poly differentiate() const {
    int n = size(); vector<mint> ans(n);
    for(int i = 1; i < size(); i++) ans[i - 1] = coef(i) * i;
    return ans;
  }
  poly integrate() const {
    int n = size(); vector<mint> ans(n + 1);
    for(int i = 0; i < size(); i++) ans[i + 1] = coef(i) / (i + 1);