Method operator +

Math/Subset Sum Problem.cpp:149–155

    return 1;
  }   
  poly operator + (const poly &x) const {
    int n = max(size(), x.size());
    vector<mint> ans(n);
    for(int i = 0; i < n; i++) ans[i] = coef(i) + x.coef(i);
    while ((int)ans.size() && ans.back() == 0) ans.pop_back();
    return ans;
  }
  poly operator - (const poly &x) const {
    int n = max(size(), x.size());
    vector<mint> ans(n);