Method operator[]

Math/Subset Sum Problem.cpp:144–144

  int size() const { return (int)a.size(); }
  inline mint coef(const int i) const { return (i < a.size() && i >= 0) ? a[i]: mint(0); }
  mint operator[](const int i) const { return (i < a.size() && i >= 0) ? a[i]: mint(0); } //Beware!! p[i] = k won't change the value of p.a[i]
  bool is_zero() const {
    for (int i = 0; i < size(); i++) if (a[i] != 0) return 0;
    return 1;