递推公式黑科技

//递推公式黑科技
#include<bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define PB push_back
#define MP make_pair
#define MEM(x,y) memset(x,y,sizeof(x));
#define bug(x) cout<<"bug"<<x<<endl;
typedef long long ll;
typedef pair<int,int> pii;
using namespace std;
const int maxn=1e3+10;
const int mod=998244353;
ll powmod(ll a,ll b){
    ll res=1;a%=mod;
    assert(b>=0);
    for(;b;b>>=1){
        if(b&1)res=res*a%mod;a=a*a%mod;
    }
    return res;
}
// head
namespace linear_seq {
    const int N=10010;
    ll res[N],base[N],_c[N],_md[N];
    vector<int> Md;
    void mul(ll *a,ll *b,int k) {
        for(int i=0;i<k+k;i++) _c[i]=0;
        for(int i=0;i<k;i++)
            if (a[i])
                for(int j=0;j<k;j++) _c[i+j]=(_c[i+j]+a[i]*b[j])%mod;
        for (int i=k+k-1;i>=k;i--)
            if (_c[i])
                for(int j=0;j<Md.size();j++)
                    _c[i-k+Md[j]]=(_c[i-k+Md[j]]-_c[i]*_md[Md[j]])%mod;
        for(int i=0;i<k;i++) a[i]=_c[i];
    }
    int solve(ll n,vector<int> a,vector<int> b) {
    // a 系数 b 初值 b[n+1]=a[0]*b[n]+...
        ll ans=0,pnt=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;
        Md.clear();
        for(int i=0;i<k;i++) if (_md[i]!=0) Md.push_back(i);
        for(int i=0;i<k;i++) res[i]=base[i]=0;
        res[0]=1;
        while ((1ll<<pnt)<=n) pnt++;
        for (int p=pnt;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<Md.size();j++) res[Md[j]]=(res[Md[j]]-res[k]*_md[Md[j]])%mod;
            }
        }
        for(int i=0;i<k;i++) ans=(ans+res[i]*b[i])%mod;
        if (ans<0) ans+=mod;
        return ans;
    }
    vector<int> BM(vector<int> s) {
        vector<int> C(1,1),B(1,1);
        int L=0,m=1,b=1;
        for(int n=0;n<s.size();n++) {
            ll d=0;
            for(int i=0;i<L+1;i++) d=(d+(ll)C[i]*s[n-i])%mod;
            if (d==0) ++m;
            else if (2*L<=n) {
                vector<int> T=C;
                ll c=mod-d*powmod(b,mod-2)%mod;
                while (C.size()<B.size()+m) C.PB(0);
                for(int i=0;i<B.size();i++) C[i+m]=(C[i+m]+c*B[i])%mod;
                L=n+1-L; B=T; b=d; m=1;
            } else {
                ll c=mod-d*powmod(b,mod-2)%mod;
                while (C.size()<B.size()+m) C.PB(0);
                for(int i=0;i<B.size();i++) C[i+m]=(C[i+m]+c*B[i])%mod;
                ++m;
            }
        }
        return C;
    }
    int gao(vector<int> a,ll n) {
        vector<int> 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,vector<int>(a.begin(),a.begin()+c.size()));
    }
};

int main(){
    ll t,n;
//    cin>>t;
    while(cin>>n){
        cout<<(linear_seq::gao(vector<int>{5,13,34,89},n-1)%mod-1)%mod<<endl;
    }
}

原文地址:https://www.cnblogs.com/bryce1010/p/9387171.html