PHP采用所有组合

Question

我看到了这个algorithm that will take numbers or words and find all possible combinations

我正在使用它，但它并没有返回所有的“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"; 
    }
?>

然后返回：

cat dog
dog cat
cat fish
fish cat
dog fish
fish dog

但这些并不都是实数组合，所有的实数组合也包括这些：

cat cat
dog dog
fish fish

这就是我所需要的，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

Answer 1

好的，这是你的代码(顺便说一句，谢谢你发布了一个如此有趣和具有挑战性的问题--至少对我来说是这样……:-)) -对给定元素数组的所有可能的排列(按N)使用递归的)

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

Answer 2

您当前的代码给了您排列，只需添加重复项：

foreach($words as $w) {
    echo "$w $w\n";    
}

有什么问题吗？