Generally speaking, the topic will not be useless, and there is nothing wrong with the topic. ....
Is the second question about the allocation table?
Let me see.
1, take a multiple of 3 twice, and the possibility is 2/6*2/6= 1/9.
2. Twice is not a multiple of 3, where 1, 4 divided by 3 is 1, and 2,5 divided by 3 is 2, so it can only be counted as (1, 2)( 1, 5) (2,4) (4,5) before and after the exchange.
Finally, 1/3. .....