具体方式请参考《算法导论》课程（开始于29分30秒）：
https://www.bilibili.com/video/av11928034/?p=3

class Solution {
public:

    struct Matrix {
        int a11, a12, a21, a22;
    };

    Matrix mul(Matrix m1, Matrix m2) {
        return {
            m1.a11 * m2.a11 + m1.a12 * m2.a21, m1.a11 * m2.a12 + m1.a12 * m2.a22,
            m1.a21 * m2.a11 + m1.a22 * m2.a21, m1.a21 * m2.a12 + m1.a22 *m2.a22
        };
    }

    Matrix pow(Matrix m, int n) {
        if(n == 0) return {
            1, 0,
            0, 1
        };

        auto temp = pow(m, n / 2);

        temp = mul(temp, temp);
        if(n % 2) temp = mul(temp, m);

        return temp;
    }

    int Fibonacci(int n) {
        if(n == 0) return 0;
        if(n == 1) return 1;

        Matrix m = {
            0, 1,
            1, 1
        };

        auto temp = pow(m, n - 1);

        return temp.a22;
    }
};