数学方法-推公式---------

解题思路:

注意事项:

参考代码:

#include<iostream>

using namespace std;

const int N = 1010;

int a[N];

int main()

{

    int n;

    while (scanf("%d", &n), n != 0)

    {

        a[1] = 1, a[2] = 2, a[3] = 3, a[4] = 4;

        if (n <= 4)    cout << a[n] << endl;

        else

        {

            for (int i = 5; i <= n; i++)

            {

                 a[i] = a[i - 3] + a[i - 1];   

            }

            cout << a[n] << endl;

        }   

    }

    return 0;

}