def common_elem_set(my_set):
   for index, val in enumerate(my_set):
      for j, k in enumerate(my_set[index + 1:], index + 1):

         if val & k:
            my_set[index] = val.union(my_set.pop(j))
            return common_elem_set(my_set)
   return my_set

my_list = [[18, 14, 12, 19], [9, 6, 2, 1], [54, 32, 21, 17], [18, 11, 13, 12]]

print("列表是：")
print(my_list)

my_set = list(map(set, my_list))

my_result = common_elem_set(my_set)

print("结果是：")
print(my_result)

列表是 ：
[[18, 14, 12, 19], [9, 6, 2, 1], [54, 32, 21, 17], [18, 11, 13, 12]]
结果是：
[{11, 12, 13, 14, 18, 19}, {9, 2, 6, 1}, {32, 17, 21, 54}]