产生随机整数的具有非均匀分布的阵列 [英] Generate an array of random integers with non-uniform distribution

问题描述

我想编写Java code产生随机整数数组范围为[1,4]。数组的长度为N，它在运行时提供。问题是，该范围[1,4]不是均匀分布：

I want to write Java code to produce an array of random integers in the range [1,4]. The array's length is N, which is provided at run time. The problem is that the range [1,4] is not uniformly distributed:

这意味着，如果我创建阵列具有N = 100，数​​字1将在一个阵列，数出现平均40次2的10倍，并依此类推。

It means that if I create arrays with N=100, the number '1' will appear averagely 40 times in an array, number '2' 10 times, and so on.

现在我用这code的范围内产生均匀分布的随机数[1,4]：

For now I am using this code to generate uniform-distributed random numbers in range [1,4]:

public static void main(String[] args)
    {
        int N;
        System.out.println();
        System.out.print("Enter an integer number: ");
        N = input.nextInt();
        int[] a = new int[N];
        Random generator = new Random();
        for(int i = 0; i < a.length; i++)
        {
            a[i] = generator.nextInt(4)+1;
        }
    }

怎样与实现它的非均匀分布，如图中上面的曲线图

How do I implement it with a the non-uniform distribution as shown in the graph above?

推荐答案

下面是一个办法做到这一点，从code启动：

Here's a way to do it, starting from your code:

public static void main(String[] args){
    int N;
    System.out.println();
    System.out.print("Enter an integer number: ");
    N = input.nextInt();
    int[] a = new int[N];
    Random generator = new Random();
    for (int i = 0; i < a.length; i++) {
        float n = generator.nextFloat();
        if (n <= 0.4) {
            a[i] = 1;
        } else if (n <= 0.7) {
            a[i] = 3;
        } else if (n <= 0.9) {
            a[i] = 4;
        } else {
            a[i] = 2;
        }
    }
}

更新：在@pjs的建议，在desdencing概率高的顺序选择号码所以你往往会更早退出if块

UPDATE: at @pjs' suggestion, select numbers in order of desdencing probability so you tend to exit the if block earlier

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