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  • 杜教BM(解决线性递推式的模板)

    前提:公式必须是线性的,前几项越多越好,一般不低于8项,不然推出来不准确。

    #include <bits/stdc++.h>
    using namespace std;
    typedef long long ll;
    typedef long long ll;
    typedef vector<int> VI;
    const int maxn = 10005;
    const ll mod = 1e9 + 7;
    const int INF = 0x3f3f3f3f;
    const double eps = 1e-9;
    
    ll fast_mod(ll a, ll n, ll Mod)
    {
        ll ans = 1;
        a %= Mod;
        while (n)
        {
            if (n & 1)
                ans = (ans * a) % Mod;
            a = (a * a) % Mod;
            n >>= 1;
        }
        return ans;
    }
    
    namespace linear_seq
    {
    ll res[maxn], base[maxn], num[maxn], md[maxn]; //数组大小约10000
    vector<int> vec;
    void mul(ll *a, ll *b, int k)
    {
        for (int i = 0; i < 2 * k; i++)
            num[i] = 0;
        for (int i = 0; i < k; i++)
        {
            if (a[i])
                for (int j = 0; j < k; j++)
                    num[i + j] = (num[i + j] + a[i] * b[j]) % mod;
        }
        for (int i = 2 * k - 1; i >= k; i--)
        {
            if (num[i])
                for (int j = 0; j < vec.size(); j++)
                    num[i - k + vec[j]] = (num[i - k + vec[j]] - num[i] * md[vec[j]]) % mod;
        }
        for (int i = 0; i < k; i++)
            a[i] = num[i];
    }
    ll solve(ll n, VI a, VI b)
    {
        ll ans = 0, cnt = 0;
        int k = a.size();
        assert(a.size() == b.size());
        for (int i = 0; i < k; i++)
            md[k - 1 - i] = -a[i];
        md[k] = 1;
        vec.clear();
        for (int i = 0; i < k; i++)
            if (md[i])
                vec.push_back(i);
        for (int i = 0; i < k; i++)
            res[i] = base[i] = 0;
        res[0] = 1;
        while ((1LL << cnt) <= n)
            cnt++;
        for (int p = cnt; p >= 0; p--)
        {
            mul(res, res, k);
            if ((n >> p) & 1)
            {
                for (int i = k - 1; i >= 0; i--)
                    res[i + 1] = res[i];
                res[0] = 0;
                for (int j = 0; j < vec.size(); j++)
                    res[vec[j]] = (res[vec[j]] - res[k] * md[vec[j]]) % mod;
            }
        }
        for (int i = 0; i < k; i++)
            ans = (ans + res[i] * b[i]) % mod;
        if (ans < 0)
            ans += mod;
        return ans;
    }
    VI BM(VI s)
    {
        VI B(1, 1), C(1, 1);
        int L = 0, m = 1, b = 1;
        for (int i = 0; i < s.size(); i++)
        {
            ll d = 0;
            for (int j = 0; j < L + 1; j++)
                d = (d + (ll)C[j] * s[i - j]) % mod;
            if (d == 0)
                m++;
            else if (2 * L <= i)
            {
                VI T = C;
                ll c = mod - d * fast_mod(b, mod - 2, mod) % mod;
                while (C.size() < B.size() + m)
                    C.push_back(0);
                for (int j = 0; j < B.size(); j++)
                    C[j + m] = (C[j + m] + c * B[j]) % mod;
                L = i + 1 - L, B = T, b = d, m = 1;
            }
            else
            {
                ll c = mod - d * fast_mod(b, mod - 2, mod) % mod;
                while (C.size() < B.size() + m)
                    C.push_back(0);
                for (int j = 0; j < B.size(); j++)
                    C[j + m] = (C[j + m] + c * B[j]) % mod;
                m++;
            }
        }
        return C;
    }
    int gao(VI a, ll n)
    {
        VI c = BM(a);
        c.erase(c.begin());
        for (int i = 0; i < c.size(); i++)
            c[i] = (mod - c[i]) % mod;
        return solve(n, c, VI(a.begin(), a.begin() + c.size()));
    }
    } // namespace linear_seq
    
    int main()
    {
        //freopen("in.txt", "r", stdin);
        //填数字的时候带上模数之后的
        ll t, n;
        scanf("%d", &t);
        while (t--)
        {
            scanf("%lld", &n);
            //在vi中填入自己推的数 8个以上 越多越好
            printf("%lld
    ", linear_seq::gao(VI{3, 9, 20, 46, 106, 244, 560, 1286, 2956, 6794}, n-1));
        }
        return 0;
    }
    当初的梦想实现了吗,事到如今只好放弃吗~
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  • 原文地址:https://www.cnblogs.com/caijiaming/p/12462385.html
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