Java抽奖算法第二例

Java抽奖算法第二例

本文实例为大家分享了java抽奖算法，供大家参考，具体内容如下

1. 算法分析

 根据概率将奖品划分区间，每个区间代表一个奖品，然后抽取随机数，反查落在那个区间上，即为所抽取的奖品。

2. 代码

核心算法

public class Arithmetic {

// 放大倍数

private static final int mulriple = 1000000;

public int pay(List prizes) {

int lastScope = 0;

// 洗牌，打乱奖品次序

Collections.shuffle(prizes);

Map prizeScopes = new HashMap();

Map prizeQuantity = new HashMap();

for (Prize prize : prizes) {

int prizeId = prize.getPrizeId();

// 划分区间

int currentScope = lastScope + prize.getProbability().multiply(new BigDecimal(mulriple)).intValue();

prizeScopes.put(prizeId, new int[] { lastScope + 1, currentScope });

prizeQuantity.put(prizeId, prize.getQuantity());

lastScope = currentScope;

}

// 获取1-1000000之间的一个随机数

int luckyNumber = new Random().nextInt(mulriple);

int luckyPrizeId = 0;

// 查找随机数所在的区间

if ((null != prizeScopes) && !prizeScopes.isEmpty()) {

Set> entrySets = prizeScopes.entrySet();

for (Map.Entry m : entrySets) {

int key = m.getKey();

if (luckyNumber >= m.getValue()[0] && luckyNumber <= m.getValue()[1] && prizeQuantity.get(key) > 0) {

http:// luckyPrizeId = key;

break;

}

}

}

if (luckyPrizeId > 0) {

// 奖品库存减一

}

return luckyPrizeId;

}

}

Prize bean

public class Prize {

/**

* 奖品唯一标示

*/

private Integer prizeId;

/**

* 中奖概率

*/

private BigDecimal probability;

/**

* 奖品数量

*/

private Integer quantity;

public Integer getPrizeId() {

return prizeId;

}

public void setPrizeId(Integer prizeId) {

this.prizeId = prizeId;

}

public BigDecimal getProbability() {

return probability;

}

public void setProbability(BigDecimal probability) {

thiYeXwPs.probability = probability;

}

public Integer getQuantity() {

return quantity;

}

public void setQuantity(Integer quantity) {

this.quantity = quantity;

}

}

3. 测试

prize1概率: 5% 

prize2概率: 10%

prize3概率: 15% 

prize4概率: 20%

prize5概率: 50%

public class Test {

public static void main(String[] args) {

List prizes = new ArrayList();

Prize prize1 = new Prize();

prize1.setPrizeId(1);

prize1.setProbability(new BigDecimal(0.05));

prize1.setQuantity(1);

prizes.add(prize1);

Prize prize2 = new Prize();

prize2.setPrizeId(2);

prize2.setProbability(new BigDecimal(0.10));

prize2.setQuantity(10);

prizes.add(prize2);

Prize prize3 = new Prize();

prize3.setPrizeId(3);

prize3.setProbability(new BigDecimal(0.15));

prize3.setQuantity(20);

prizes.add(prize3);

Prize prize4 = new Prize();

prize4.setPrizeId(4);

prize4.setProbability(new BigDecimal(0.20));

prize4.setQuantity(50);

prizes.add(prize4);

Prize prize5 = new Prize();

prize5.setPrizeId(5);

prize5.setProbability(new BigDecimal(0.50));

prize5.setQuantity(200);

prizes.add(prize5);

int prize1GetTimes = 0;

int prize2GetTimes = 0;

int prize3GetTimes = 0;

int prize4GetTimes = 0;

int prize5GetTimes = 0;

Arithmetic arithmetic = new Arithmetic();

int times = 1000;

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

int prizeId = arithmetic.pay(prizes);

switch (prizeId) {

case 1:

prize1GetTimes++;

break;

case 2:

http:// prize2GetTimes++;

break;

case 3:

prize3GetTimes++;

break;

case 4:

prize4GetTimes++;

break;

case 5:

prize5GetTimes++;

break;

}

}

System.out.println("抽奖次数" + times);

System.out.println("prize1中奖次数" + prize1GetTimes);

System.out.println("prize2中奖次数" + prize2GetTimes);

System.out.println("prize3中奖次数" + prize3GetTimes);

System.out.println("prize4中奖次数" + prize4GetTimes);

System.out.println("prize5中奖次数" + prize5GetTimes);

}

}

结果：

通过1000次抽取，我们看出算法精度还是很高的。

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。