hdu 4291 A Short problem

http://acm.hdu.edu.cn/showproblem.php?pid=4291

找循环节 + 矩阵连乘

代码：

#include <iostream>

#include <cstdio>

#include <cstring>

#include <queue>

#include <vector>

#include <algorithm>



#define LL long long

//#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const LL MOD=1000000007;

const LL K1=222222224;

const LL K2=183120;

LL a[2][2];

LL ans[2];

void Renew(LL M)

{

    LL temp[2];

    temp[0]=(ans[0]*a[0][0])%M+(ans[1]*a[1][0])%M;

    temp[1]=(ans[0]*a[0][1])%M+(ans[1]*a[1][1])%M;

    ans[0]=temp[0]%M;

    ans[1]=temp[1]%M;

}

void Kmul(LL M)

{

    LL temp[2][2];

    temp[0][0]=(a[0][0]*a[0][0])%M+(a[0][1]*a[1][0])%M;

    temp[0][1]=(a[0][0]*a[0][1])%M+(a[0][1]*a[1][1])%M;

    temp[1][0]=(a[1][0]*a[0][0])%M+(a[1][1]*a[1][0])%M;

    temp[1][1]=(a[1][0]*a[0][1])%M+(a[1][1]*a[1][1])%M;

    a[0][0]=temp[0][0]%M;a[0][1]=temp[0][1]%M;

    a[1][0]=temp[1][0]%M;a[1][1]=temp[1][1]%M;

}

LL Save(LL n,int M)

{

    a[0][0]=3;a[0][1]=1;

    a[1][0]=1;a[1][1]=0;

    ans[0]=1;ans[1]=0;

    while(n)

    {

        if(n&1)

        {

            Renew(M);

        }

        Kmul(M);

        n=n>>1;

    }

    n=ans[1];

    return n;

}

int main()

{

    //freopen("data.txt","r",stdin);

    LL n;

    while(cin>>n)

    {

      cout<<Save(Save(Save(n,K2),K1),MOD)<<endl;

    }

    return 0;

}