我猜“分成 $k$ 类”这句话隐含了每类非空 （
by dengyaotriangle @ 2021-07-04 19:24:38
每类非空吧
by s_r_f @ 2021-07-04 19:29:36
@[syksykCCC](/user/51971) ~~不行，素质差~~
by hongzy @ 2021-07-04 22:40:10