多数组求笛卡尔积

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/*--------------------------------------
*+多数组求笛卡尔积
*--------------------------------------
*/
　　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}。

function Descartes() {

    $t = func_get_args();    if(func_num_args() == 1){        return call_user_func_array( __FUNCTION__, $t[0] );    }    $a = array_shift($t);    if(! is_array($a)){        $a = array($a);    }    $a = array_chunk($a, 1);    do {        $r = array();        $b = array_shift($t);        if(! is_array($b)){            $b = array($b);        }        foreach($a as $p){            foreach(array_chunk($b, 1) as $q){                $r[] = array_merge($p, $q);            }        }        $a = $r;    }while($t);        return $r;}//示例$arr = array(    array('a1','a2','a3'),    'b',    array('c1','c2'),    array('d1','d2','d3'),    //......省略其它元素（也可以是数组），);$r = Descartes( $arr );var_dump($r);exit;/*array(18) {  [0]=>  array(4) {    [0]=>    string(2) "a1"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d1"  }  [1]=>  array(4) {    [0]=>    string(2) "a1"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d2"  }  [2]=>  array(4) {    [0]=>    string(2) "a1"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d3"  }  [3]=>  array(4) {    [0]=>    string(2) "a1"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d1"  }  [4]=>  array(4) {    [0]=>    string(2) "a1"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d2"  }  [5]=>  array(4) {    [0]=>    string(2) "a1"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d3"  }  [6]=>  array(4) {    [0]=>    string(2) "a2"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d1"  }  [7]=>  array(4) {    [0]=>    string(2) "a2"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d2"  }  [8]=>  array(4) {    [0]=>    string(2) "a2"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d3"  }  [9]=>  array(4) {    [0]=>    string(2) "a2"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d1"  }  [10]=>  array(4) {    [0]=>    string(2) "a2"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d2"  }  [11]=>  array(4) {    [0]=>    string(2) "a2"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d3"  }  [12]=>  array(4) {    [0]=>    string(2) "a3"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d1"  }  [13]=>  array(4) {    [0]=>    string(2) "a3"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d2"  }  [14]=>  array(4) {    [0]=>    string(2) "a3"    [1]=>    string(1) "b"    [2]=>    string(2) "c1"    [3]=>    string(2) "d3"  }  [15]=>  array(4) {    [0]=>    string(2) "a3"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d1"  }  [16]=>  array(4) {    [0]=>    string(2) "a3"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d2"  }  [17]=>  array(4) {    [0]=>    string(2) "a3"    [1]=>    string(1) "b"    [2]=>    string(2) "c2"    [3]=>    string(2) "d3"  }}*/

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