Question

我正在尝试根据用户提供的特定范围打印五个永不重复的随机数字。以下是我到目前为止的代码。我昨晚问了一个类似的问题并得到了一些很好的答案，但现在我只想使用数组和循环来完成这个。感谢。

package h1p2;

public class test{
    public void method (int min, int max){
        //Declare and initialize arrays and index variables
        int rangeOne[];
        int rangeMinMax[];
        rangeOne = new int[5];
        rangeMinMax = new int[max - min];
        int z = min;
        int i = 0;
        int q = 0;
        int rangeLength = rangeMinMax.length;



        //need minimum/max differential of 50 or > to execute method
        if (max - min < 50){
            System.out.println("Please enter numbers with a differential of 50 or greater.");
        }

        //run if differential checks out
        else{
            //populate MinMax array with range specified by user
            while (i < rangeLength){
                rangeMinMax[i] = z;
                z++;
                i++;
            }
        }

        //pick random number from MinMax array
        int randomNumber = (rangeMinMax[(int) (rangeLength * Math.random())]);
        int r = 0;
        //populate rangeOne array with lotto numbers, forbidding duplicates
        while (r < 5){
            randomNumber = (rangeMinMax[(int) (rangeLength * Math.random())]);
            rangeOne[r] = randomNumber;
            randomNumber = (rangeMinMax[(int) (rangeLength * Math.random())]);
            if (r == 1 && randomNumber == rangeOne[0]){
                r--;
            }

            if (r == 2 && (randomNumber == rangeOne[0] || randomNumber == rangeOne[1])){
                r--;
            }

            if (r == 3 && (randomNumber == rangeOne[0] || randomNumber == rangeOne[1] || 
                    randomNumber == rangeOne[2])){
                r--;
            }

            if (r == 4 && (randomNumber == rangeOne[0] || randomNumber == rangeOne[1] || 
                    randomNumber == rangeOne[2] || randomNumber == rangeOne[3])){
                r--;
            }
            else{
            r++;}
        }

        //create string with results
        String results = Integer.toString(rangeOne[0]) + " " + Integer.toString(rangeOne[1])
                + " " + Integer.toString(rangeOne[2]) + " " + Integer.toString(rangeOne[3]) +
                " " + Integer.toString(rangeOne[4]);

        //print results
        System.out.println("MegaNumbers: " + results);
    }

}

Answer 1

如果您只需要少量数字，只需使用线性搜索来模拟一组。然后继续生成随机数，直到您生成足够的唯一数字就足够了。显然这不是最有效的，但很简单。

private static Random rand = new Random();

public static boolean contains(int [] data, int value)
{
    for (int i = 0; i < data.length; i++)
    {
        if (data[i] == value)
        {
            return true;
        }
    }

    return false;
}

public static int[] getRandom(int size, int lowerBound, int upperBound)
{
    if (upperBound - lowerBound <= size)
    {
        throw new IllegalArgumentException("Range is too small!");
    }

    int totalRandoms = 0;

    int[] randoms = new int[size];

    while (totalRandoms != size)
    {
        int randNumber = rand.nextInt(upperBound - lowerBound) + lowerBound;
        if (! contains(randoms, randNumber))
        {
            randoms[totalRandoms] = randNumber;
        }
    }

    return randoms;
}

P.S。我已经把一些细节留给了你，我刚刚提供了几个非OO函数来让你对可能的算法有所了解。

Answer 2

我写了randomList（）来接受三个参数：

1）最小随机值

2）最大随机值

3）以及数组应具有的随机值的数量。

该方法首先创建一个名为choices的数组，其中包含从最小值到最大值的所有值。然后它启动一个循环，用来自选择的值填充新数组。每当循环从选择中选择一个随机值时，它会将该值移动到choices数组的后面并更新lastIndex，这样它就不再从选择的后面选择任何值。

更简单的方法是选择一个ArrayList并简单地从中删除已经获取的值。但是因为我们不能使用ArrayLists，所以这段代码应该可以正常工作。

public static int[] randomList(int min, int max, int number) {
    // fills an array with all numbers from min to max
    int[] choices = new int[max - min + 1];
    int lastIndex = choices.length - 1;
    for(int i = min; i <= max; i++) {
        choices[i - min] = i;
    }

    // fills the new array with values from choices
    Random r = new Random();
    int[] randomList = new int[number];
    for(int i = 0; i < number; i++) {
        int index = r.nextInt(lastIndex + 1); 
        randomList[i] = choices[index];
        int copy = choices[lastIndex];
        choices[lastIndex] = randomList[i];
        choices[index] = copy;
        lastIndex--;
    }
    return randomList;
}

使用循环和数组在Java中生成随机数列表

2 个答案: