PHP 接受所有组合

我看到了这个算法将采用数字或单词并找到所有可能的组合 https://stackoverflow.com/questions/1256117/algorithm-that-will-take-numbers-or-words-and-find-all-possible-combinations

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

但这些并不都是真实的组合，所有真实的组合还包括这些：

cat cat
dog dog
fish fish

这就是我需要的，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，感谢您发布如此有趣且具有挑战性的问题 - 至少对我来说......:-)） -使用递归对于给定元素数组的所有可能的排列（按 N））

Code :

<?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);

?>

Output :

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
)

HINT : By permutations($words,2)，你将能够得到你想要的......