求代码

用怎样的代码将m个数分成n份，其中每份中的数相加小于z，不考虑每组内的顺序以及组与组之间的顺序，并输出所有可能组合，示例：

已知：$words = Array
(
[0] => 1
[1] => 2
[2] => 3
)
$n = 2,$z=5
要得到：Array
(
[0] => 2|13
[1] => 3|12
)


已知：$words = Array
(
[0] => 1
[1] => 2
[2] => 3
)
$n = 3,$z=5
要得到：Array
(
[0] => 1|2|3
)


已知：$words = Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
)
$n = 2,$z=7
要得到：Array
(
[0] => 4|123
[1] => 13|24
[2] => 14|23
)