基于概率的PHP数组中随机项的选取

Question

我有一张用户地图和他们为抽奖(或彩票或其他类似活动)购买的入场券数量。

用户到条目的地图位于结构中，如下所示：

// Map the person to the amount of entries they have purchased
$entries = [
    'Adam' => 5,
    'James' => 3,
    'Oliver' => 4,
    'Holly' => 8
];

我想选择一个随机的用户，但考虑到他们的机会，根据票计数。获胜的可能性必须是：

(用户票金额/票务总数)* 100 =概率百分比

例如，从测试阵列的预期结果是霍莉将赢得8次抽奖20次。

Answer 1

这是一个巧合，你是问这个，因为我创造了一个方法，就这样做，就在前几天，当为一个投注网站编写脚本。

请参阅评论意见，说明守则的组成如下：

// The array passed to the function should be your $entries array
function randProb(array $items) {
  $totalProbability = 0; // This is defined to keep track of the total amount of entries

  foreach ($items as $item => $probability) {
      $totalProbability += $probability;     
  }

  $stopAt = rand(0, $totalProbability); // This picks a random entry to select
  $currentProbability = 0; // The current entry count, when this reaches $stopAt the winner is chosen

  foreach ($items as $item => $probability) { // Go through each possible item
      $currentProbability += $probability; // Add the probability to our $currentProbability tracker
      if ($currentProbability >= $stopAt) { // When we reach the $stopAt variable, we have found our winner
          return $item;
      }
  }

  return null;
}

如果您想输出获胜项目的值(概率)，请在断点返回$probability，而不是$item。

Answer 2

这应该能做你想做的事情，而且很容易理解。

function rand_with_entries($entries) {

    //create a temporary array
    $tmp = [];

    //loop through all names
    foreach($entries as $name => $count) {

        //for each entry for a specific name, add name to `$tmp` array
        for ($x = 1; $x <= $count; $x++) {
            $tmp[] = $name;
        }

    }

    //return random name from `$tmp` array
    return $tmp[array_rand($tmp)];
}

Answer 3

好的，您有这样的数据：

$entries = [
    'Adam' => 5,
    'James' => 3,
    'Oliver' => 4,
    'Holly' => 8
];

一种方法是根据这些数据填充数组并使用array_rand。以下是一个例子：

function pickRand($array, $nb) {
    $newArray = [];
    foreach ($array as $name => $probability) {
        $num = $probability;
        while ($num > 0) {
            $newArray[] = $name;
            $num--;
        }
    }
    return $newArray[array_rand($newArray, $nb)];
}

并利用它：

$randomName = pickRand($entries, 1);