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
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);
}
# <a href="/tag/suiji/" target="_blank" class="keywords">随机</a>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);
}