hdu1575 矩阵快速幂 模板题

传送门

题意：求给定n维方阵的k次幂后的对角线元素和

思路：模板题

代码如下：

#include 
int N;//N个系数，N维矩阵
typedef long long ll;
using namespace std;
struct matrix
{
    int m[20][20];
};
matrix ans, base, m;
matrix multi(matrix a, matrix b,ll mod,int N)
{
    matrix tmp;
    for (int i = 0; i < N; ++i)
    {
        for (int j = 0; j < N; ++j)
        {
            tmp.m[i][j] = 0;
            for (int k = 0; k < N; ++k)
                tmp.m[i][j] = (tmp.m[i][j] + (a.m[i][k] * b.m[k][j])) % mod;
        }
    }
    return tmp;
}




matrix fastm(matrix base, ll n,ll mod,int N)
{
    int i = 0, j = 0;
    matrix ans;
    memset(ans.m, 0, sizeof(ans.m));
        for (i = 0; i < N; i++)
            ans.m[i][i] = 1;
    while (n)
    {
        if (n & 1)
        {
            ans = multi(ans, base,mod,N);
        }
        base = multi(base, base,mod,N);
        n >>= 1;
    }
    return ans;
}
int main()
{
    ll k,mod=9973, sum=0 ;
    matrix m, ans;
    int t;cin>>t;
    while(t--)
    {
        sum=0;
        int n,k;
        cin>>n>>k;
        N=n;
        for(int i=0;i>m.m[i][j];
        }

        ans = fastm(m,k,mod,n);

        for (int i = 0; i < N; i++)
            sum += ans.m[i][i];
        printf("%d\n", sum%mod);

    }

    return 0;
}