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 ); } |