modint 板子

自动对 int 取模

// modint
template<int MOD> struct Fp {
    ll val;
    constexpr Fp(ll v = 0) noexcept : val(v % MOD) { if (val < 0) val += MOD; }
    constexpr int getmod() const { return MOD; }
    constexpr Fp operator - () const noexcept { return val ? MOD - val : 0; }
    constexpr Fp operator + (const Fp &r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp &r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp &r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp &r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp &operator += (const Fp &r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp &operator -= (const Fp &r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp &operator *= (const Fp &r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp &operator /= (const Fp &r) noexcept {
        ll a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            ll t = a / b;
            a -= t * b, swap(a, b);
            u -= t * v, swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator < (const Fp &r) const noexcept { return this->val < r.val; }
    constexpr bool operator == (const Fp &r) const noexcept { return this->val == r.val; }
    constexpr bool operator != (const Fp &r) const noexcept { return this->val != r.val; }
    friend constexpr istream &operator >> (istream &is, Fp<MOD> &x) noexcept {
        is >> x.val;
        x.val %= MOD;
        if (x.val < 0) x.val += MOD;
        return is;
    }
    friend constexpr ostream &operator << (ostream &os, const Fp<MOD> &x) noexcept { return os << x.val; }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &r, ll n) noexcept {
        if (n == 0) return 1;
        if (n < 0) return modpow(modinv(r), -n);
        auto t = modpow(r, n / 2);
        t = t * t;
        if (n & 1) t = t * r;
        return t;
    }
    friend constexpr Fp<MOD> modinv(const Fp<MOD> &r) noexcept {
        ll a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            ll t = a / b;
            a -= t * b, swap(a, b);
            u -= t * v, swap(u, v);
        }
        return Fp<MOD>(u);
    }
};

const int MOD = 998244353;
using mint = Fp<MOD>;