改变获得随机数的概率 [英] changing probability of getting a random number

问题描述

我想生成一个0和3之间的随机数，我在代码中有以下内容：

I would like to generate a random number between 0 and 3 and I have the following in my code:

int random = rand() % 4;

这很好，但我想它大多数时间生成1,2和3 0只是偶尔。

This works fine but I would like it to generate 1, 2, and 3 most of the time and 0 only occasionally.

这是最好的方法是什么？解决这个问题的常用算法的名称是什么？

What is the best way to go about this? What are the names of common algorithms to address this problem?

推荐答案

假设你想要0,1,2,3有5％，20％，30％，45％的分布。

你可以这样做：

Here's one way. Suppose you want 0, 1, 2, 3 to have a distribution of 5%, 20%, 30%, 45%.
You could do it like this:

double val = (double)rand() / RAND_MAX;

int random;
if (val < 0.05)       //  5%
    random = 0;
else if (val < 0.25)  //  5% + 20%
    random = 1;
else if (val < 0.55)  //  5% + 20% + 30%
    random = 2;
else
    random = 3;

当然，它不必使用浮点。我只是这样做，因为它更直观。

Of course it doesn't have to be done with floating-point. I just did it this way since it's more intuitive.

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