微信红包

package com.aifocus.data.collection.service.pdd;

import java.util.ArrayList;
import java.util.List;

/**
 * 微信随机分配红包算法
 *
 * @author leo-zeng
 *
 */
public class RedEnvelopesDemo {
    private static final float MINMONEY = 0.5f;
    private static final float MAXMONEY = 20;

    private boolean isRight(float money, int count) {
        double avg = money / count;
        if (avg < MINMONEY) {
            return false;
        } else if (avg > MAXMONEY) {
            return false;
        }
        return true;
    }

    private float randomRedPacket(float money, float mins, float maxs, int count) {
        if (count == 1) {
            return (float) (Math.round(money * 100)) / 100;
        }
        if (mins == maxs) {
            return mins;//如果最大值和最小值一样，就返回mins
        }
        float max = maxs > money ? money : maxs;
        float one = ((float) Math.random() * (max - mins) + mins);
        one = (float) (Math.round(one * 100)) / 100;
        float moneyOther = money - one;
        if (isRight(moneyOther, count - 1)) {
            return one;
        } else {
            //重新分配
            float avg = moneyOther / (count - 1);
            if (avg < MINMONEY) {
                return randomRedPacket(money, mins, one, count);
            } else if (avg > MAXMONEY) {
                return randomRedPacket(money, one, maxs, count);
            }
        }
        return one;
    }

    private static final float TIMES = 2.1f;

    public List<Float> splitRedPackets(float money, int count) {
        if (!isRight(money, count)) {
            return null;
        }
        List<Float> list = new ArrayList<Float>();
        float max = (float) (money * TIMES / count);

        max = max > MAXMONEY ? MAXMONEY : max;

        //这里时循环的，可以改一下，这个代码。
        for (int i = 0; i < count; i++) {
            float one = randomRedPacket(money, MINMONEY, max, count - i);
            list.add(one);
            money -= one;
            System.out.println(one);
        }
        return list;
    }

    public static void main(String[] args) {

        RedEnvelopesDemo util = new RedEnvelopesDemo();

        float totalMoney = 100;//总金额
        int count = 20;//个数
        float max = (float) (totalMoney * TIMES / count);
        for (int i =1 ; i < count+1; i++){

            float one =util.randomRedPacket(totalMoney, MINMONEY, max, count - i);
            totalMoney -=one;
        }
        System.out.println(totalMoney);





      //  RedEnvelopesDemo util = new RedEnvelopesDemo();
        List<Float> list = util.splitRedPackets(100, 20);
        float  a = 0;
        for (Float aa : list) {
            a=a+aa;
        }
        System.out.println(a);
    }

}