Java模拟发红包三种算法

以下为测试代码


public class Test {
    public static void main(String[] args) {
        getRed(1000, 10);
        getRed(10, 10, 0.01);
        cut(1000, 10);
    }

    //二倍均值法
    public static void getRed(int totalAmount, int totalPeopleNum) {
        List<Integer> amountList = new ArrayList<Integer>();
        Integer restAmount = totalAmount;
        Integer restPeopleNum = totalPeopleNum;
        Random random = new Random();
        //随机范围：[1，剩余人均金额的两倍)，左闭右开
        int min = 1;
        for (int i = 0; i < totalPeopleNum - 1; i++) {
            int amount = random.nextInt(restAmount / restPeopleNum * 2 - 1) + 1;
            amount = amount <= min ? min : amount;
            restAmount -= amount;
            restPeopleNum--;
            amountList.add(amount);
        }
        amountList.add(restAmount);

        for (int count = 1; count <= amountList.size(); count++) {
            System.out.println("第" + count + "个人拿到" + new BigDecimal(amountList.get(count - 1)).divide(new BigDecimal(100)));
        }
        System.out.println("1、本轮发红包中第" + (amountList.indexOf(Collections.max(amountList)) + 1) + "个人手气最佳");
    }

    //最大最小值法
    public static void getRed(int totalPeopleNum, float totalAmount, double min) {
        float money;
        double max;
        int i = 1;
        List math = new ArrayList();
        DecimalFormat df = new DecimalFormat("###.##");
        while (i < totalPeopleNum) {
            //保证即使一个红包是最大的了,后面剩下的红包,每个红包也不会小于最小值
            max = totalAmount - min * (totalPeopleNum - i);
            int k = (int) (totalPeopleNum - i) / 2;
            //保证最后两个人拿的红包不超出剩余红包
            if (totalPeopleNum - i <= 2) {
                k = totalPeopleNum - i;
            }
            //最大的红包限定的平均线上下
            max = max / k;
            //保证每个红包大于最小值,又不会大于最大值
            money = (int) (min * 100 + Math.random() * (max * 100 - min * 100 + 1));
            money = (float) money / 100;
            //保留两位小数
            money = Float.parseFloat(df.format(money));
            totalAmount = (int) (totalAmount * 100 - money * 100);
            totalAmount = totalAmount / 100;
            math.add(money);
            System.out.println("第" + i + "个人拿到" + money);
            i++;
            //最后一个人拿走剩下的红包
            if (i == totalPeopleNum) {
                math.add(totalAmount);
                System.out.println("第" + i + "个人拿到" + totalAmount);
            }
        }
        //取数组中最大的一个值的索引
        System.out.println("2、本轮发红包中第" + (math.indexOf(Collections.max(math)) + 1) + "个人手气最佳");
    }

    //  线段切割法
    public static void cut(int totalAmount, int totalPeopleNum) {
        //验证参数合理校验
        //为了使用random.nextInt(Integer)方法不得不先把红包金额放大100倍，最后在main函数里面再除以100
        //这样就可以保证每个人抢到的金额都可以精确到小数点后两位
        int fen = totalAmount;
        if (fen < totalPeopleNum || totalPeopleNum < 1) {
            System.out.println("红包个数必须大于0，并且最小红包不少于1分");
        }
        List<Integer> boards = new ArrayList<>();
        boards.add(0);
        boards.add(fen);
        //红包个数和板砖个数的关系
        while (boards.size() <= totalPeopleNum) {
            int index = new Random().nextInt(fen - 1) + 1;
            if (boards.contains(index)) {
                //保证板子的位置不相同
                continue;
            }
            boards.add(index);
        }
        //计算每个红包的金额，将两个板子之间的钱加起来
        Collections.sort(boards);
        List<Integer> list = new ArrayList<>();
        for (int i = 0; i < boards.size() - 1; i++) {
            Integer e = boards.get(i + 1) - boards.get(i);
            list.add(e);
        }
        int i = 1;
        for (int count = 1; count <= list.size(); count++) {
            System.out.println("第" + count + "个人拿到" + new BigDecimal(list.get(count - 1)).divide(new BigDecimal(100)));
        }
        System.out.println("3、本轮发红包中第" + (list.indexOf(Collections.max(list)) + 1) + "个人手气最佳");
    }
}