有效地从 PHP 数组中选取 n 个随机元素(无随机播放) [英] Efficiently pick n random elements from PHP array (without shuffle)

问题描述

我有以下代码从 PHP 中的数组 $array 中选取 $n 元素:

I have the following code to pick $n elements from an array $array in PHP:

shuffle($array);
$result = array_splice($array, 0, $n);

给定一个大数组但只有几个元素(例如 10000 中的 5)，这相对较慢，所以我想优化它，使其不所有元素都必须打乱.这些值必须是唯一的.

Given a large array but only a few elements (for example 5 out of 10000), this is relatively slow, so I would like to optimize it such that not all elements have to be shuffled. The values must be unique.

我正在寻找性能最高的替代方案.我们可以假设 $array 没有重复项并且是 0 索引.

I'm looking fo the most performant alternative. We can assume that $array has no duplicates and is 0-indexed.

推荐答案

$randomArray = [];
while (count($randomArray) < 5) {
  $randomKey = mt_rand(0, count($array)-1);
  $randomArray[$randomKey] = $array[$randomKey];
}

这将提供 5 个没有重复的元素并且非常快.密钥将被保留.

This will provide exactly 5 elements with no duplicates and very quickly. The keys will be preserved.

注意:您必须确保 $array 有 5 个或更多元素，或者添加某种检查以防止无限循环.

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