如何在PHP中找到每个可能的数组组合

Question

$data = array(
'a' => array('a1', 'a2', 'a3'),
'b' => array('b1', 'b2', 'b3', 'b4'),
'c' => array('c1', 'c2', 'c3', 'c4', 'c5'));

要得到

a1
a2
a3
b1
b2
b3
b4
c1
c2
c3
c4
c5

a1 b1
a1 b2
a1 b3
a1 b4
a1 c1
a1 c2
a1 c3
a1 c4
a1 c5

b1 c1
b1 c2
b1 c3
b1 c4
b1 c5
b2 c1
b2 c2
b2 c3
b2 c4
b2 c5
b3 c1
b3 c2
b3 c3
b3 c4
b3 c5
b4 c1
b4 c2
b4 c3
b4 c4
b4 c5

a1 b1 c1
a1 b1 c2
a1 b1 c3
a1 b1 c4
a1 b1 c5
a1 b2 c1
a1 b2 c2
a1 b2 c3
a1 b2 c4
a1 b2 c5
a1 b3 c1
a1 b3 c2
a1 b3 c3
a1 b3 c4
a1 b3 c5
a1 b4 c1
a1 b4 c2
a1 b4 c3
a1 b4 c4
a1 b4 c5
etc...

谢谢

Answer 1

显然你想构建几个数组的笛卡尔积,即每个元素与其他元素相结合.

此外,您希望有结果元组省略一个或多个这些数组,为简单起见,我会建模为null每个数组中都有一个元素:

$result = array(array()); // We need to start with one element already, because thats the identity element of the cartesian product
foreach ($data as $arr)
{
    array_push($arr,null); // Add a null element to the array to get tuples with less than all arrays

    // This is the cartesian product:
    $new_result = array();
    foreach ($result as $old_element)
        foreach ($arr as $el)
            $new_result []= array_merge($old_element,array($el));
    $result = $new_result;
}

请注意,你的结果行a1 b3 c2的代码给你array('a1','b3','c2')和你的结果行b4 c3的代码给你array('b4','c3',null).