51Nod 1242 斐波那契数列的第N项（矩阵快速幂）

#include <iostream>
#include <algorithm>
using namespace std;

typedef long long LL;
const int maxn = 2;
const LL m = 1000000009;

struct Matrix
{
    LL v[maxn][maxn];
};

//矩阵间的乘法
Matrix matrix_mul(Matrix A, Matrix B){
    Matrix ans;
    for (int i = 0; i < maxn; i++){
        for (int j = 0; j < maxn; j++){
            ans.v[i][j] = 0;
            for (int k = 0; k < maxn; k++){
                ans.v[i][j] += (A.v[i][k] * B.v[k][j]) % m;
            }
            ans.v[i][j] %= m;
        }
    }
    return ans;
}

Matrix matrix_pow(Matrix C, LL n){
    Matrix ans = { 1, 0, 0, 1 };
    while (n){
        if (n & 1){
            ans = matrix_mul(ans, C);
        }
        C = matrix_mul(C, C);
        n >>= 1;
    }
    return ans;
}

int main(){
    ios::sync_with_stdio(false);

    LL n;
    cin >> n;
    Matrix e = { 1, 0, 1, 0 };
    Matrix ee = { 1, 1, 1, 0 };
    Matrix ans = matrix_pow(ee, n - 1);
    ans = matrix_mul(e, ans);
    cout << ans.v[0][0] << endl;
    //system("pause");
    return 0;
}