Hdu-6470 Count(簡單構造矩陣）

公式：$f(n)=f(n-1)+2*f(n-1)+n^3$

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long ll;
const int Max_n=6;
const int mod=123456789;

int n=6;
struct Mat{
	ll m[Max_n][Max_n];
	Mat(){memset(m,0,sizeof(m));}
	Mat(ll s[6][6]){
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++)
			m[i][j]=s[i][j];
		}
	}
	Mat operator*(Mat &a){
		Mat b;
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				for(int k=0;k<n;k++)
				b.m[i][j]=(b.m[i][j]+m[i][k]*a.m[k][j])%mod;
			}
		}
		return b;
	}
};

Mat quickMod(Mat base,ll exp){
	Mat ans;
	for(int i=0;i<n;i++)ans.m[i][i]=1;
	while(exp){
		if(exp&1)ans=ans*base;
		exp>>=1;
		base=base*base;
	}
	return ans;
}


int main()
{
	ll s[6][6]={
		{1,2,1,3,3,1},
		{1,0,0,0,0,0},
		{0,0,1,3,3,1},
		{0,0,0,1,2,1},
		{0,0,0,0,1,1},
		{0,0,0,0,0,1}
	};
	int t;ll k;
	cin>>t;
	while(t--){
		scanf("%lld",&k);
		Mat base(s);
		Mat mat=quickMod(base,k-2);
		ll a[6]={2,1,8,4,2,1};
		ll sum=0;
		for(int i=0;i<6;i++){
			sum=(sum+mat.m[0][i]*a[i])%mod;
		}
		cout<<sum<<endl;
	}
	return 0;
}