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Fft

c++

long long mod_inv(long long a, long long mod){
    // a^{-1} = 1/a mod p (拡張Euclidの互除法)
    long long b = mod, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= mod;
    if (u < 0) u += mod;
    return u;
}
long long mod_pow(long long a, long long n, long long mod){
    long long ret = 1;
    long long p = a % mod;
    while(n){
        if(n&1) ret = ret * p % mod;
        p = p * p % mod;
        n >>= 1;
    }
    return ret;
}


template<int mod, int primitive_root>
class NTT {
public:
    int get_mod() const { return mod; }
    void _ntt(vector<long long>& a, int sign) {
        const int n = a.size();
        assert((n ^ (n&-n)) == 0); //n = 2^k

        const int g = 3; //g is primitive root of mod
        int h = (int)mod_pow(g, (mod - 1) / n, mod); // h^n = 1
        if (sign == -1) h = (int)mod_inv(h, mod); //h = h^-1 % mod

        //bit reverse
        int i = 0;
        for (int j=1; j<n-1; ++j) {
            for (int k = n >> 1; k >(i ^= k); k >>= 1);
            if (j < i) swap(a[i], a[j]);
        }

        for (int m=1; m<n; m*=2) {
            const int m2 = 2 * m;
            const long long base = mod_pow(h, n / m2, mod);
            long long w = 1;
            for(int x=0; x<m; x++) {
                for (int s = x; s < n; s += m2) {
                    long long u = a[s];
                    long long d = a[s + m] * w % mod;
                    a[s] = u + d;
                    if (a[s] >= mod) a[s] -= mod;
                    a[s + m] = u - d;
                    if (a[s + m] < 0) a[s + m] += mod;
                }
                w = w * base % mod;
            }
        }

        for (auto& x : a) if (x < 0) x += mod;
    }
    void ntt(vector<long long>& input) {
        _ntt(input, 1);
    }
    void intt(vector<long long>& input) {
        _ntt(input, -1);
        const int n_inv = mod_inv(input.size(), mod);
        for (auto& x : input) x = x * n_inv % mod;
    }

    // 畳み込み演算を行う
    vector<long long> convolution(const vector<long long>& a, const vector<long long>& b){
        int ntt_size = 1;
        while (ntt_size < (int)(a.size()+b.size())) ntt_size *= 2;

        vector<long long> _a = a, _b = b;
        _a.resize(ntt_size); _b.resize(ntt_size);

        ntt(_a);
        ntt(_b);

        for(int i=0; i<ntt_size; i++){
            (_a[i] *= _b[i]) %= mod;
        }

        intt(_a);
        return _a;
    }
};

typedef NTT<167772161,3> NTT_1;
typedef NTT<469762049,3> NTT_2;
typedef NTT<1224736769,3> NTT_3;

// garnerのアルゴリズムを直書きしたversion,速い
vector<long long> int32mod_convolution(vector<long long> a, vector<long long> b,int mod){
    for (auto& x : a) x %= mod;
    for (auto& x : b) x %= mod;

    NTT_1 ntt1; NTT_2 ntt2; NTT_3 ntt3;
    assert(ntt1.get_mod() < ntt2.get_mod() && ntt2.get_mod() < ntt3.get_mod());
    auto x = ntt1.convolution(a, b);
    auto y = ntt2.convolution(a, b);
    auto z = ntt3.convolution(a, b);

    // garnerのアルゴリズムを極力高速化した
    const long long m1 = ntt1.get_mod(), m2 = ntt2.get_mod(), m3 = ntt3.get_mod();
    const long long m1_inv_m2 = mod_inv(m1, m2);
    const long long m12_inv_m3 = mod_inv(m1 * m2, m3);
    const long long m12_mod = m1 * m2 % mod;
    vector<long long> ret(x.size());
    for(int i=0; i<(int)x.size(); i++){
        long long v1 = (y[i] - x[i]) *  m1_inv_m2 % m2;
        if (v1 < 0) v1 += m2;
        long long v2 = (z[i] - (x[i] + m1 * v1) % m3) * m12_inv_m3 % m3;
        if (v2 < 0) v2 += m3;
        long long constants3 = (x[i] + m1 * v1 + m12_mod * v2) % mod;
        if (constants3 < 0) constants3 += mod;
        ret[i] = constants3;
    }

    return ret;
}

//2^23より大きく,primitive rootに3を持つもの
// const int mods[] = { 1224736769, 469762049, 167772161, 595591169, 645922817, 897581057, 998244353 };