关于微信红包的算法

每个人抢到的金额比较平均的算法

 

package com.example.demo.money;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class SnatchMoney {

    //二倍均值法
    public static List divideRedPackage(Integer totalAmount,
                                                 Integer totalPeopleNum) {
        List amountList = new ArrayList();
        //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
        Integer restAmount = totalAmount * 100;
        Integer restPeopleNum = totalPeopleNum;
        Random random = new Random();
        for (int i = 0; i < totalPeopleNum - 1; i++) {
            // 随机范围：[1，剩余人均金额的两倍)，左闭右开
            int amount = random.nextInt(restAmount / restPeopleNum * 2 - 1) + 1;
            restAmount -= amount;
            restPeopleNum--;
            amountList.add(amount);
        }
        amountList.add(restAmount);
        return amountList;
    }

    //随机金额法
    private static List divide(double money, int n) {
        //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 = (int) (money * 100);
        if (fen < n || n < 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 boards = new ArrayList<>();
        boards.add(0);
        boards.add(fen);
        //红包个数和板砖个数的关系
        while (boards.size() <= n) {
            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 list = new ArrayList<>();
        for (int i = 0; i < boards.size() - 1; i++) {
            Integer e = boards.get(i + 1) - boards.get(i);
            list.add(e);
        }
        return list;

    }
    public static void main(String[] args) {
//        List accountList = divideRedPackage(50, 1000);
        List accountList = divideRedPackage(100, 10);
        BigDecimal count = new BigDecimal(0);
        for (Integer amount : accountList) {
            //将抢到的金额再除以100进行还原
            BigDecimal tmpcount = new BigDecimal(amount).divide(new BigDecimal(100));
            count = count.add(tmpcount);
            System.out.println("抢到金额：" + tmpcount);

        }
        System.out.println("total=" + count);
    }
}