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
<?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);
}
}
/**
* 简单的抽奖类
*/
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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