递归求阶乘和

https://pintia.cn/problem-sets/12/problems/352

double fact(int n)
{
    double product;
    if (n == 0)
    {
        product = 1;
    }
    else
    {
        product = n * fact(n - 1);
    }

    return product;
}
double factsum(int n)
{
    double result = 0;
    for (int i = 1; i <= n; i++)
    {
        result = result + fact(i);
    }

    return result;
}