广工赛-hdu6470矩阵快速幂

递推时把(n+1)^3拆开 构造矩阵即可

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 123456789
struct Mat{
    ll m[][];
    Mat(){memset(m,,sizeof m);}
}A;
ll n,F[];
void mul(Mat A,ll F[]){
    ll B[]={};
    for(int i=;i<;i++)
        for(int j=;j<;j++)
            B[i]=(B[i]+A.m[i][j]*F[j]%mod)%mod;
    memcpy(F,B,sizeof B);
}
void mulself(Mat & A,Mat B){
    Mat C;
    for(int i=;i<;i++)
        for(int j=;j<;j++)
            for(int k=;k<;k++)
                C.m[i][j]=(C.m[i][j]+A.m[i][k]*B.m[k][j]%mod)%mod;
    memcpy(A.m,C.m,sizeof C.m);
}
int main(){
    int T;
    cin>>T;
    while(T--){
        F[]=,F[]=,F[]=,F[]=,F[]=,F[]=;
        memset(A.m,,sizeof A.m);
        A.m[][]=;
        A.m[][]=;A.m[][]=;A.m[][]=;
        A.m[][]=;A.m[][]=;A.m[][]=;A.m[][]=;
        A.m[][]=;A.m[][]=;A.m[][]=;
        A.m[][]=;A.m[][]=;
        A.m[][]=;
        cin>>n;
        n-=;
        while(n){
            if(n%)
                mul(A,F);
            mulself(A,A);
            n>>=;
        }
        cout<<F[]%mod<<'\n';
    }
}