C++实现斐波那契数列

#include <iostream>
using namespace std;

int main()
{
    int a[4] = {1,1,1,0};//前面讨论过
    int b[4] = {1,0,0,1};//单位阵
    int n,a1,a2,a3,a0;

    cin >> n;

    if (n == 0)
    {
        cout << "0";
        return 0;
    }
    if (n == 1)
    {
        cout << "1";
        return 1;
    }
    n = n-1;
    while ( n > 0 )
    {
        if ( n%2 == 1 )
        {
            n = n - 1;
            a0 = b[0]*a[0] + b[1]*a[2];
            a1 = b[0]*a[1] + b[1]*a[3];
            a2 = b[2]*a[0] + b[3]*a[2];//此处实际上不用更新b[2],b[3]
            a3 = b[2]*a[1] + b[3]*a[3];
            b[0] = a0;b[1] = a1;b[2] = a2;b[3] = a3;
        }
        n = n/2;
        a0 = a[0]*a[0] + a[1]*a[2];
        a1 = a[0]*a[1] + a[1]*a[3];
        a2 = a[2]*a[0] + a[3]*a[2];
        a3 = a[2]*a[1] + a[3]*a[3];
        a[0] = a0;a[1] = a1;a[2] = a2;a[3] = a3;
    }

    cout << b[0];
    return 0;
}