package com.example.ant.common.tools;

import java.util.LinkedList;

import java.util.List;

/**

* 描述：红包算法

* User: 曾远征

* Date: 2018-09-17

* Time: 14:09

*/

public class RedPacketTools {

/**

* 生成红包最小值 1分

*/

private static final int MIN_MONEY = 1;

/**

* 生成红包最大值 200人民币

*/

private static final int MAX_MONEY = 200 * 100;

/**

* 小于最小值

*/

private static final int LESS = -1;

/**

* 大于最大值

*/

private static final int MORE = -2;

/**

* 正常值

*/

private static final int OK = 1;

/**

* 最大的红包是平均值的 TIMES 倍，防止某一次分配红包较大

*/

private static final double TIMES = 2.1F;

private int recursiveCount = 0;

private List splitRedPacket(int money, int count) {

List moneys = new LinkedList<>();

//计算出最大红包

int max = (int) ((money / count) * TIMES);

max = max > MAX_MONEY ? MAX_MONEY : max;

for (int i = 0; i < count; i++) {

//随机获取红包

int redPacket = randomRedPacket(money, MIN_MONEY, max, count - i);

moneys.add(redPacket);

//总金额每次减少

money -= redPacket;

}

return moneys;

}

private int randomRedPacket(int totalMoney, int minMoney, int maxMoney, int count) {

//只有一个红包直接返回

if (count == 1) {

return totalMoney;

}

if (minMoney == maxMoney) {

return minMoney;

}

//如果最大金额大于了剩余金额 则用剩余金额 因为这个 money 每分配一次都会减小

maxMoney = maxMoney > totalMoney ? totalMoney : maxMoney;

//在 minMoney到maxMoney 生成一个随机红包

int redPacket = (int) (Math.random() * (maxMoney - minMoney) + minMoney);

int lastMoney = totalMoney - redPacket;

int status = checkMoney(lastMoney, count - 1);

//正常金额

if (OK == status) {

return redPacket;

}

//如果生成的金额不合法 则递归重新生成

if (LESS == status) {

recursiveCount++;

System.out.println("recursiveCount==" + recursiveCount);

return randomRedPacket(totalMoney, minMoney, redPacket, count);

}

if (MORE == status) {

recursiveCount++;

System.out.println("recursiveCount===" + recursiveCount);

return randomRedPacket(totalMoney, redPacket, maxMoney, count);

}

return redPacket;

}

/**

* 校验剩余的金额的平均值是否在 最小值和最大值这个范围内

*

* @param lastMoney

* @param count

* @return

*/

private int checkMoney(int lastMoney, int count) {

double avg = lastMoney / count;

if (avg < MIN_MONEY) {

return LESS;

}

if (avg > MAX_MONEY) {

return MORE;

}

return OK;

}

public static void main(String[] args) {

RedPacketTools redPacket = new RedPacketTools();

List redPackets = redPacket.splitRedPacket(20000, 100);

System.out.println(redPackets);

int sum = 0;

for (Integer red : redPackets) {

sum += red;

}

System.out.println(sum);

}

}