获取PHP数组的所有排列？

Question

给定PHP字符串数组,例如:

['peter', 'paul', 'mary']

如何生成此数组元素的所有可能排列？即:

peter-paul-mary
peter-mary-paul
paul-peter-mary
paul-mary-peter
mary-peter-paul
mary-paul-peter

Answer 1

function pc_permute($items, $perms = array()) {
    if (empty($items)) { 
        echo join(' ', $perms) . "<br />";
    } else {
        for ($i = count($items) - 1; $i >= 0; --$i) {
             $newitems = $items;
             $newperms = $perms;
             list($foo) = array_splice($newitems, $i, 1);
             array_unshift($newperms, $foo);
             pc_permute($newitems, $newperms);
         }
    }
}

$arr = array('peter', 'paul', 'mary');

pc_permute($arr);

要么

function pc_next_permutation($p, $size) {
    // slide down the array looking for where we're smaller than the next guy
    for ($i = $size - 1; $p[$i] >= $p[$i+1]; --$i) { }

    // if this doesn't occur, we've finished our permutations
    // the array is reversed: (1, 2, 3, 4) => (4, 3, 2, 1)
    if ($i == -1) { return false; }

    // slide down the array looking for a bigger number than what we found before
    for ($j = $size; $p[$j] <= $p[$i]; --$j) { }

    // swap them
    $tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp;

    // now reverse the elements in between by swapping the ends
    for (++$i, $j = $size; $i < $j; ++$i, --$j) {
         $tmp = $p[$i]; $p[$i] = $p[$j]; $p[$j] = $tmp;
    }

    return $p;
}

$set = split(' ', 'she sells seashells'); // like array('she', 'sells', 'seashells')
$size = count($set) - 1;
$perm = range(0, $size);
$j = 0;

do { 
     foreach ($perm as $i) { $perms[$j][] = $set[$i]; }
} while ($perm = pc_next_permutation($perm, $size) and ++$j);

foreach ($perms as $p) {
    print join(' ', $p) . "\n";
}

http://docstore.mik.ua/orelly/webprog/pcook/ch04_26.htm

Answer 2

这可以满足您的需要,即无需分配任何额外的内存.它将结果排列存储在$ results数组中.我非常有信心这是解决任务的禁食方式.

<?php
function computePermutations($array) {
    $result = [];

    $recurse = function($array, $start_i = 0) use (&$result, &$recurse) {
        if ($start_i === count($array)-1) {
            array_push($result, $array);
        }

        for ($i = $start_i; $i < count($array); $i++) {
            //Swap array value at $i and $start_i
            $t = $array[$i]; $array[$i] = $array[$start_i]; $array[$start_i] = $t;

            //Recurse
            $recurse($array, $start_i + 1);

            //Restore old order
            $t = $array[$i]; $array[$i] = $array[$start_i]; $array[$start_i] = $t;
        }
    };

    $recurse($array);

    return $result;
}


$results = computePermutations(array('foo', 'bar', 'baz'));
print_r($results);

这适用于PHP> 5.4.我使用匿名函数进行递归以保持主函数的接口清洁.

Answer 3

我对杰克的答案进行了一些扩展

function pc_permute($items, $perms = [],&$ret = []) {
   if (empty($items)) {
       $ret[] = $perms;
   } else {
       for ($i = count($items) - 1; $i >= 0; --$i) {
           $newitems = $items;
           $newperms = $perms;
           list($foo) = array_splice($newitems, $i, 1);
           array_unshift($newperms, $foo);
           $this->pc_permute($newitems, $newperms,$ret);
       }
   }
   return $ret;
}

这实际上将返回一个包含所有可能排列的数组。

$options = ['startx','starty','startz','endx','endy','endz'];
$x = $this->pc_permute($options);
var_dump($x);

  [0]=>
 array(6) {
    [0]=>
    string(6) "startx"
    [1]=>
    string(6) "starty"
    [2]=>
    string(6) "startz"
    [3]=>
    string(4) "endx"
    [4]=>
    string(4) "endy"
    [5]=>
    string(4) "endz"
  }
  [1]=>
  array(6) {
    [0]=>
    string(6) "starty"
    [1]=>
    string(6) "startx"
    [2]=>
    string(6) "startz"
    [3]=>
    string(4) "endx"
    [4]=>
    string(4) "endy"
    [5]=>
    string(4) "endz"
  }
  [2]=>
  array(6) {
    [0]=>
    string(6) "startx"
    [1]=>
    string(6) "startz"
    [2]=>
    string(6) "starty"
    [3]=>
    string(4) "endx"
    [4]=>
    string(4) "endy"
    [5]=>
    string(4) "endz"
  }
  [3]=>
  array(6) {
    [0]=>
    string(6) "startz"
    [1]=>
    string(6) "startx"
    [2]=>
    string(6) "starty"
    [3]=>
    string(4) "endx"
    [4]=>
    string(4) "endy"
    [5]=>
    string(4) "endz"
  }
  [4]=>
  array(6) {
    [0]=>
    string(6) "starty"
    [1]=>
    string(6) "startz"
    [2]=>
    string(6) "startx"
    [3]=>
    string(4) "endx"
    [4]=>
    string(4) "endy"
    [5]=>
    string(4) "endz"
  }
  [5]=>
  array(6) {
    [0]=>
    string(6) "startz"
    [1]=>
    string(6) "starty"
    [2]=>
    string(6) "startx"
    [3]=>
    string(4) "endx"
    [4]=>
    string(4) "endy"
    [5]=>
    string(4) "endz"
  }
  [6]=> ................ a lot more

我发现返回数组而不是字符串更有用。然后由使用应用程序如何处理结果（加入它们，或其他）

Answer 4

我需要类似的东西,一边看一边发现这篇文章.着手写下以下工作.

有8个项目它的工作速度相当快(比我在网上找到的例子快一点),但超出了这个范围,运行时间迅速增加.如果您只需输出结果,则可以更快地制作,并大大减少内存使用量.

print_r(AllPermutations(array('peter', 'paul', 'mary')));

function AllPermutations($InArray, $InProcessedArray = array())
{
    $ReturnArray = array();
    foreach($InArray as $Key=>$value)
    {
        $CopyArray = $InProcessedArray;
        $CopyArray[$Key] = $value;
        $TempArray = array_diff_key($InArray, $CopyArray);
        if (count($TempArray) == 0)
        {
            $ReturnArray[] = $CopyArray;
        }
        else
        {
            $ReturnArray = array_merge($ReturnArray, AllPermutations($TempArray, $CopyArray));
        }
    }
    return $ReturnArray;
}

请注意,排列数是数组中项目数的阶乘.3个项目有6个排列,4个有24个,5个有1​​20个,6个有720个等.