矩阵

const ll maxn = 10;
struct Matrix {
    ld a[maxn][maxn];
    int n;
    Matrix (int sz, int kind) {
        this->n = sz;
        for (int i = 0; i < sz; i ++) {
            for (int j = 0; j < sz; j ++) {
                a[i][j] = 0;
            }
        }
        for (int i = 0; i < sz; i ++) {
            a[i][i] = kind;
        }
    }
    Matrix operator*(Matrix rhs)const {
        Matrix ret(N - 1, 0);
        for (int i  = 0; i < n; i ++) {
            for (int j = 0; j < n; j ++) {
                for (int k = 0; k < n; k ++) {
                    ret.a[i][j] += a[i][k] * rhs.a[k][j];
                }
            }
        }
        return ret;
    }
    void out() {
        for (int i = 0; i < 5 ;i ++) {
            for (int j = 0; j < 5; j ++) {
                cout << a[i][j] << " ";
            }
            cout << endl;
        }
    }
} A(maxn - 1, 0);
Matrix q_pow( int k) {//注意不要带矩阵参数很容易爆栈
    Matrix ret = {N - 1, 1};
    Matrix x = A;
    while (k) {
        if (k & 1) {
            ret = ret * x;
        }
        k >>= 1;
        x = x * x;
    }
    return ret;
}