双色球&大乐透中奖概率

/// <summary>
/// 阶乘
/// </summary>
/// <param name="number"></param>
/// <returns></returns>
static double N(int number)
{
    double result = 1;
    for (int i = 1; i <= number; i++)
    {
        result *= i;
    }
    return result;
}

/// <summary>
/// 排列
/// </summary>
/// <param name="n"></param>
/// <param name="m"></param>
/// <returns></returns>
static double P(int n, int m)
{
    //return N(n) / N(n - m);
    double result = 1;
    for (int i = n; i > n - m; i--)
    {
        result *= i;
    }
    return result;
}

/// <summary>
/// 组合
/// </summary>
/// <param name="n"></param>
/// <param name="m"></param>
/// <returns></returns>
static double C(int n, int m)
{
    return P(n, m) / N(m);
}