P1962 斐波那契数列

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int Mod = 1e9 + 7;
int n;
struct Node {
    int a[5][5] {};
    friend Node operator*(Node a, Node b) {
        Node ans;
        for (int i = 1; i <= 2; i++)
            for (int j = 1; j <= 2; j++)
                for (int k = 1; k <= 2; k++)
                    ans.a[i][j] += a.a[i][k] * b.a[k][j], ans.a[i][j] %= Mod;
        return ans;
    }
} ans, b;
signed main() {
    cin >> n;
    if (n <= 2) {
        cout << 1 << endl;
        return 0;
    }

    b.a[1][1] = b.a[1][2] = b.a[2][1] = 1;
    ans.a[1][1] = ans.a[1][2] = 1;
    n -= 2;
    while (n) {
        if (n & 1) ans = ans * b;
        b = b * b;
        n = n >> 1;
    }
    cout << ans.a[1][1] << endl;
}