test/yosupo/find_linear_recurrence.test.cpp

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Last update: 2024-01-07 20:09:47+09:00
Problem: https://judge.yosupo.jp/problem/find_linear_recurrence

Depends on

Code

#define PROBLEM "https://judge.yosupo.jp/problem/find_linear_recurrence"

#include "../../math/modint.hpp"
#include "../../math/berlekamp_massey.cpp"


#include <bits/stdc++.h>
using namespace std;

using mint = Modint<998244353>;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;
    vector<mint> a(N);
    for (auto& x : a) cin >> x;
    auto ans = berlekamp_massey(a);
    cout << ans.size() << endl;
    for (int i = 0; i < ans.size(); ++i) {
        cout << ans[i];
        if (i < (int) ans.size() - 1) cout << " ";
    }
    cout << endl;
}

#line 1 "test/yosupo/find_linear_recurrence.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/find_linear_recurrence"

#line 2 "math/modint.hpp"
#include <algorithm>
#include <iostream>

/**
 * @brief Mod int
 */
template <int m>
class Modint {
    using mint = Modint;
    static_assert(m > 0, "Modulus must be positive");

   public:
    static constexpr int mod() { return m; }

    constexpr Modint(long long y = 0) : x(y >= 0 ? y % m : (y % m + m) % m) {}

    constexpr int val() const { return x; }

    constexpr mint& operator+=(const mint& r) {
        if ((x += r.x) >= m) x -= m;
        return *this;
    }
    constexpr mint& operator-=(const mint& r) {
        if ((x += m - r.x) >= m) x -= m;
        return *this;
    }
    constexpr mint& operator*=(const mint& r) {
        x = static_cast<int>(1LL * x * r.x % m);
        return *this;
    }
    constexpr mint& operator/=(const mint& r) { return *this *= r.inv(); }

    constexpr bool operator==(const mint& r) const { return x == r.x; }

    constexpr mint operator+() const { return *this; }
    constexpr mint operator-() const { return mint(-x); }

    constexpr friend mint operator+(const mint& l, const mint& r) {
        return mint(l) += r;
    }
    constexpr friend mint operator-(const mint& l, const mint& r) {
        return mint(l) -= r;
    }
    constexpr friend mint operator*(const mint& l, const mint& r) {
        return mint(l) *= r;
    }
    constexpr friend mint operator/(const mint& l, const mint& r) {
        return mint(l) /= r;
    }

    constexpr mint inv() const {
        int a = x, b = m, u = 1, v = 0;
        while (b > 0) {
            int t = a / b;
            std::swap(a -= t * b, b);
            std::swap(u -= t * v, v);
        }
        return mint(u);
    }

    constexpr mint pow(long long n) const {
        mint ret(1), mul(x);
        while (n > 0) {
            if (n & 1) ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }

    friend std::ostream& operator<<(std::ostream& os, const mint& r) {
        return os << r.x;
    }

    friend std::istream& operator>>(std::istream& is, mint& r) {
        long long t;
        is >> t;
        r = mint(t);
        return is;
    }

   private:
    int x;
};
#line 2 "math/berlekamp_massey.cpp"
#include <vector>

template <typename T>
std::vector<T> berlekamp_massey(const std::vector<T>& a) {
    int n = a.size();
    std::vector<T> B = {1}, C = {1};
    T b = 1;
    int L = 0, m = 1;
    for (int i = 0; i < n; ++i) {
        T d = a[i];
        for (int j = 1; j < (int) C.size(); ++j) {
            d += a[i-j] * C[j];
        }
        if (d == 0) {
            ++m;
        } else {
            auto tmp =  C;
            if (C.size() < m + B.size()) {
                C.resize(m + B.size());
            }
            T f = d / b;
            for (int j = 0; j < (int) B.size(); ++j) {
                C[m + j] -= f * B[j];
            }
            if (2 * L <= i) {
                L = i + 1 - L;
                b = d;
                B = tmp;
                m = 1;
            } else {
                ++m;
            }
        }
    }
    std::vector<T> ret(L);
    for (int i = 1; i <= L; ++i) {
        ret[i-1] = -C[i];
    }
    return ret;
}
#line 5 "test/yosupo/find_linear_recurrence.test.cpp"


#include <bits/stdc++.h>
using namespace std;

using mint = Modint<998244353>;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;
    vector<mint> a(N);
    for (auto& x : a) cin >> x;
    auto ans = berlekamp_massey(a);
    cout << ans.size() << endl;
    for (int i = 0; i < ans.size(); ++i) {
        cout << ans[i];
        if (i < (int) ans.size() - 1) cout << " ";
    }
    cout << endl;
}