php实现概率性随机抽奖代码

2025-05-29 0 95

1、初始数据:

权重越大,抽取的几率越高
[奖品1, 权重 5], [ 奖品2, 权重6], [ 奖品3, 权重 7], [ 奖品4, 权重2]

2、处理步骤:

1)N = 5 + 6 + 7 + 2 = 20
2)然后取1-N的随机数M
3)界定各 奖品的权重范围值 奖品 1 : 1-5 ; 奖品2 : 6-11; 奖品3: 12-18; 奖品4: 19-20
4) 如果M在某个奖品的权重范围值内,标识这个奖品被抽取到

?

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<?php

/**

* 奖品

*/

class Prize {

# ID

public $id = null;

# 权重

public $weight = null;

# 奖品名

public $name = null;

# 权重范围区间起始值

protected $start = 0;

# 权重范围区间结束值

protected $end = 0;

public function __construct($id, $weight, $name) {

if (!$id) {

throw new Exception('奖品ID为空.');

}

$this->id = $id;

$this->weight = $weight ? $weight : 0;

$this->name = $name ? $name : '随机奖品' . $id;

}

# id

public function getId() {

return $this->id;

}

# 权重

public function getWeight() {

return $this->weight;

}

# 设置权重范围区间

public function setRange($start, $end) {

$this->start = $start;

$this->end = $end;

}

# 判断随机数是否在权重范围区间

public function inRange($num) {

return ($num >= $this->start) && ($num <= $this->end);

}

}

/**

* 奖品池

*/

class PrizePoll implements IteratorAggregate, Countable {

# 奖品集

protected $items = array();

# 加入奖品

public function addItem(Prize $item) {

$this->items[$item->getId()] = $item;

return $this;

}

# 删除奖品

public function removeItem($itemId) {

if (isset($this->items[$itemId])) {

unset($this->items[$itemId]);

}

return $this;

}

# 更新奖品

public function updateItem(Prize $item) {

if (isset($this->items[$item->getId()])) {

$this->items[$item->getId()] = $item;

}

return $this;

}

# 获取所有奖品

public function getItems() {

return $this->items;

}

# 所有所有可用奖品(如果权重为0,说明这个奖品永远不可能抽到)

public function getVisibleItems() {

$items = array();

foreach ($this->items as $item) {

if ($item->getWeight()) {

$items[$item->getId()] = $item;

}

}

return $items;

}

# Countable::count

public function count() {

return count($this->items);

}

# IteratorAggregate::getIterator()

public function getIterator() {

return new ArrayIterator($this->items);

}

}

/**

* 简单的抽奖

*/

class SimpleTurn {

# 奖池

protected $poll = null;

public function __construct(PrizePoll $poll) {

if ($poll) {

$this->setPoll($poll);

}

}

# 抽奖

public function run(PrizePoll $poll) {

$poll = $poll ? $poll : $this->poll;

if ( ! $poll) {

throw new Exception('奖池未初始化');

}

if ($poll->count() <= 0) {

throw new Exception('奖池为空');

}

$items = $poll->getVisibleItems();

if (count($items) <= 0) {

throw new Exception('奖池为空');

}

$sum = 0;

foreach ($items as $item) {

$start = $sum + 1;

$sum += $item->getWeight();

$end = $sum;

# 设置奖品的权重范围区间

$item->setRange($start, $end);

}

# 随机数

$rand = $this->getRandNum(1, $sum);

# 区间段判断

foreach ($items as $item) {

if ($item->inRange($rand)) {

return $item;

}

}

return null;

}

# 获取随机数

public function getRandNum($min, $max) {

return mt_rand($min ? $min : 1, $max);

}

# 设置奖池

public function setPoll(PrizePoll $poll) {

$this->poll = $poll;

}

}

# 示例

try {

$prizePoll = new PrizePoll();

$prizePoll->addItem(new Prize(1, 5))

->addItem(new Prize(2, 6))

->addItem(new Prize(3, 7))

->addItem(new Prize(4, 2));

$turn = new SimpleTurn($prizePoll);

$prize = $turn->run();

var_dump($prize);

} catch (Exception $e) {

print_r($e);

}

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