BJFU 1440 fudq的ACM

矩阵快速幂

#include<cstdio>
#include<algorithm>
using namespace std;
const int Nmax = 25;
const int INF =1e9;
const int mod=1000000007;
 
long long n;
int error;
struct Matrix
{
    int n,m;
    long long map[Nmax][Nmax];
    Matrix(int x,int y)
    {
        n=x;m=y;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                map[i][j]=0;
    }
    Matrix operator * (const Matrix b)
    {
        Matrix c(n,b.m);
        if(m==b.n)
        {
            for(int i=1;i<=c.n;i++)
                for(int j=1;j<=c.m;j++)
                    for(int k=1;k<=m;k++)
                        c.map[i][j]=(c.map[i][j]+(map[i][k]*b.map[k][j])%mod)%mod;
            return c;
        }
        printf("error!!!!!!!!!!!!!!\n");   
    }
};
 
Matrix get(long long n)
{
    Matrix base(2,2);
    base.map[1][1]=2;
    base.map[1][2]=2;
    base.map[2][1]=1;
    base.map[2][2]=0;
    Matrix ans(2,2);
    ans.map[1][1]=1;
    ans.map[1][2]=0;
    ans.map[2][1]=0;
    ans.map[2][2]=1;
     
    while(n>0)
    {
        if(n & 1)
            ans=ans*base;
        base=base*base;
        n>>=1;
    }
     
    return ans;
}
 
 
 
int main()
{
    //freopen("bjfu.in","r",stdin);
    Matrix base(2,1);  
    base.map[1][1]=8;
    base.map[2][1]=3;
     
    while(scanf("%I64d",&n)==1)
    {
        if(n>=3)
        {
            Matrix ans=get(n-2);
            ans=ans*base;
            printf("%I64d\n",ans.map[1][1]);
        }
        else
        {
            printf("%I64d\n",base.map[3-n][1]);
        }
    }
    return 0;
}