java中奖率算法_抽奖概率-三种算法

在Java中，有多种方式可以实现抽奖概率算法。下面介绍三种常用的算法：

1. 按照中奖概率随机抽取

这种算法最简单直接，即根据每个奖项对应的中奖概率，生成相应的随机数，然后根据随机数的大小来判断中哪个奖项。代码示例：

public static int lottery(double[] probabilities) {
    double sum = 0;
    for (double probability : probabilities) {
        sum += probability;
    }
    double rand = Math.random() * sum;
    sum = 0;
    for (int i = 0; i < probabilities.length; i++) {
        sum += probabilities[i];
        if (rand < sum) {
            return i;
        }
    }
    return -1;
}

2. 利用累加概率进行抽取

这种算法的思路是先将每个奖项的中奖概率累加起来，然后生成一个[0,1)之间的随机数，然后根据随机数在累加概率上的位置，判断中哪个奖项。代码示例：

public static int lottery(double[] probabilities) {
    double[] cumProbabilities = new double[probabilities.length];
    cumProbabilities[0] = probabilities[0];
    for (int i = 1; i < probabilities.length; i++) {
        cumProbabilities[i] = cumProbabilities[i - 1] + probabilities[i];
    }
    double rand = Math.random();
    for (int i = 0; i < cumProbabilities.length; i++) {
        if (rand < cumProbabilities[i]) {
            return i;
        }
    }
    return -1;
}

3. 利用二分查找进行抽取

这种算法的思路是先将每个奖项的中奖概率累加起来，并且将累加概率对应的奖项编号存储在一个数组中。然后生成一个[0,1)之间的随机数，利用二分查找在累加概率数组上定位到对应的奖项编号。代码示例：

public static int lottery(double[] probabilities) {
    double[] cumProbabilities = new double[probabilities.length];
    cumProbabilities[0] = probabilities[0];
    for (int i = 1; i < probabilities.length; i++) {
        cumProbabilities[i] = cumProbabilities[i - 1] + probabilities[i];
    }
    double rand = Math.random();
    int index = Arrays.binarySearch(cumProbabilities, rand);
    if (index < 0) {
        index = -(index + 1);
    }
    return index;
}

这三种算法各有优缺点，可以根据实际需要选择合适的算法。