C++ 函数--幽径初探索

#include <iostream>
using namespace std;

long double probability(unsigned numbers, unsigned picks);

int main()
{
    cout << fixed;
    int total, choices;
    cout << "输入这场游戏共有多少选择的机会\n"
         << "而玩家每次能选择几次？" << endl;
    while((cin >> total >> choices) && choices <= total)
    {
        cout << "玩家参加了" << probability(total, choices) << "次活动才能赢得大奖\n"
             << "输入下两个要测试的数字(按q退出)：";
    }
    cout << "bye!" << endl;
    return 0;
}

//计算彩票中奖的概率。从numbers次机会中，取picks次
long double probability(unsigned numbers, unsigned picks)
{
    long double result = 1.0;
    unsigned n;
    unsigned p;

    for(n = numbers, p = picks; p > 0; n--, p--)
    {
        result = result * n / p;
    }
    return result;
}