我看到了这个算法，它将取数字或单词并找到所有可能的组合
我正在使用它，但它不会返回所有“真实”组合。
PHP：
<?php require_once 'Math/Combinatorics.php'; $words = array('cat', 'dog', 'fish'); $combinatorics = new Math_Combinatorics; foreach($combinatorics->permutations($words, 2) as $p) { echo join(' ', $p), "\n"; } ?>
它返回：
cat dog dog cat cat fish fish cat dog fish fish dog
但这并不是全部真实组合，所有真实组合也包括以下内容：
cat cat dog dog fish fish
这就是我需要的，用于获得所有真实组合的方法：
cat dog dog cat cat fish fish cat dog fish fish dog cat cat dog dog fish fish
好的，这是您的代码（顺便说一句，感谢您发布了这样一个有趣且具有挑战性的问题-至少对我来说… :-)）- 在给定元素数组的情况下，对所有可能的排列 使用递归 （按N））
代码：
<?php function permutations($arr,$n) { $res = array(); foreach ($arr as $w) { if ($n==1) $res[] = $w; else { $perms = permutations($arr,$n-1); foreach ($perms as $p) { $res[] = $w." ".$p; } } } return $res; } // Your array $words = array('cat','dog','fish'); // Get permutation by groups of 3 elements $pe = permutations($words,3); // Print it out print_r($pe); ?>
输出：
Array ( [0] => cat cat cat [1] => cat cat dog [2] => cat cat fish [3] => cat dog cat [4] => cat dog dog [5] => cat dog fish [6] => cat fish cat [7] => cat fish dog [8] => cat fish fish [9] => dog cat cat [10] => dog cat dog [11] => dog cat fish [12] => dog dog cat [13] => dog dog dog [14] => dog dog fish [15] => dog fish cat [16] => dog fish dog [17] => dog fish fish [18] => fish cat cat [19] => fish cat dog [20] => fish cat fish [21] => fish dog cat [22] => fish dog dog [23] => fish dog fish [24] => fish fish cat [25] => fish fish dog [26] => fish fish fish )
提示： 通过permutations($words,2)，您将完全可以得到想要的…
permutations($words,2)
