c++ - 连续创建一个0到1之间的随机数

Question

我正在尝试用 C++ 为股票价格变动建模。我需要创建一个介于 0 到 1 之间的随机数。

但似乎随机数生成器的值一直在增加，并不是真正随机的。

代码如下所示:

#include<iostream>
#include<ctime>
#include<cstdlib>
#include<time.h>

using namespace std;

int main()
{
    double stockPrice = 25;
    int start = 0, end = 0;
    start = clock();

    srand (time(NULL));
    cout << (double) rand() / (double) (RAND_MAX) << endl;
    system("pause");

    while(stockPrice > 18)
    {
        if(stockPrice == 20)
        {
            double probability = (rand()/(double)RAND_MAX);
            if(probability <= (1/10))
            {
                stockPrice = stockPrice-1;
            }
            else
            {
                stockPrice = stockPrice +1;
            }
        }
        else if (stockPrice < 20)
        {
            double probability = (rand()/(double)RAND_MAX);
            if(probability <= (1/3))
            {
                stockPrice = stockPrice -1;
            }
            else
            {
                stockPrice = stockPrice +1;
            }
        }
        else 
        {
            double probability = (rand()/(double)RAND_MAX);
            if(probability <= (2/3))
            {
                stockPrice = stockPrice -1;
            }
            else
            {
                stockPrice = stockPrice +1;
            }
        }
        cout << stockPrice << endl;
    }

    end = clock();

    double t = (double)(start-end)/CLOCKS_PER_SEC;
    cout << t << endl;
    system("pause");
}

不确定如何解决这个问题。需要一些指导...

Answer 1

Need some guidance...

指导 1:

正确的比较，你应该使用

double probability = (rand()/(double)(RAND_MAX + 1));
                                               ^
                                        for better scaling

因为当前在 if(probability <= (1/10)) 行由于转换 1/10，您正在与 0 进行比较1/3和 2/3到整数

指导 2:

毕竟你可以使用更好的生成器 statistical properties

#include <random>
#include <iostream>

    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_real_distribution<> dis(0, 1);
    double uniformOn01 = dis(gen);