給出數組(list)，生成各種可能的組合，不排序

Python自帶的itertools模塊就能實現

import itertools
nums = itertools.permutations([1,2,3])
for x in nums:
    print(x)

>>>
(1, 2, 3)
(1, 3, 2)
(2, 1, 3)
(2, 3, 1)
(3, 1, 2)
(3, 2, 1)