hdu 4291 A Short problem 夜

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;
}