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Home Backend Development PHP Tutorial 数组合并及统计新组数的元素个数

数组合并及统计新组数的元素个数

Jun 20, 2016 pm 12:59 PM

$oldArr = array(array('a','b','c','d'),array('a','b'));//组成一个新的二维数组,样式如下$newArray = array(array('a','a'),array('a','b'),array('b','a'),array('b','b'),.......array('d','b'));//$oldArry子子元素的个数未知,就是需要组成一个新的二维数组,并去掉元素相同的数组如:array('a','a'),array('b','b');
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想了一个晚上,也不知道怎么弄,还有升级的

如果$oldArr的元素是三个的话,那么$newarray子子元素的数量也是三个:

$oldArr = array(array('a','b','c','d'),array('a','b'),array('e','f','g'));$newArray = array(array('a','a','e'),array('a','a','f'),array('a','a','f'),array('a','b','e'),.......array('d','b','g'));//同样要去掉元素相同的数组,只能留下三个不同的元素,如:array('a','a','e’),array('a','a','f')
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回复讨论(解决方案)

你的基础算法是求笛卡尔积
笛卡尔(Descartes)乘积又叫直积。设A、B是任意两个集合,在集合A中任意取一个元素x,在集合B中任意取一个元素y,组成一个有序对(x,y),把这样的有序对作为新的元素,他们的全体组成的集合称为集合A和集合B的直积,记为A×B,即A×B={(x,y)|x∈A且y∈B}。
有关笛卡尔积的讨论,在精华区收录了不少,你可以去看看

鉴于你有对结果数组过滤的要求,所以取一种并用回调函数实现过滤

$oldArr = array(array('a','b','c','d'),array('a','b'));//$oldArr = array(array('a','b','c','d'),array('a','b'),array('e','f','g'));print_r(Descartes($oldArr, 'foo'));function foo($a) {  return count($a) == count(array_count_values($a));}function Descartes($d, $func='') {  $r = array_pop($d);  while($d) {    $t = array();    $s = array_pop($d);    if(! is_array($s)) $s = array($s);    foreach($s as $x) {      foreach($r as $y) {        $m = array_merge(array($x), is_array($y) ? $y : array($y));        if($func && $func($m)) $t[] = $m;      }    }    $r = $t;  }  return $r;}
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Array(    [0] => Array        (            [0] => a            [1] => b        )    [1] => Array        (            [0] => b            [1] => a        )    [2] => Array        (            [0] => c            [1] => a        )    [3] => Array        (            [0] => c            [1] => b        )    [4] => Array        (            [0] => d            [1] => a        )    [5] => Array        (            [0] => d            [1] => b        ))
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版本牛x,对的,就是求笛卡尔积

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