If nine people are divided into three groups, ABC must be in the L position, and ABC has six situations in the L position. ABC, ACB, BAC, BCA, Cab, CBA, first make sure to multiply by 6, and then the remaining six people will be divided into three groups in pairs. Probability theory selects two groups of numbers, namely C62*C42* 1/2 (considering repetition). That is to say, first count six people, combine them in pairs, and how many ways are there to divide one * * *. The three groups divided by ABC's position method can also choose six different position configurations, that is, the final answer is 6 * 6 * C62 * C42 *1/2 =1620.

The algorithm is absolutely correct. Specific considerations may not be comprehensive. Answer for reference.

The above answer is to number the teams, that is, to number the teams differently, which belongs to the full permutation algorithm. ABC is fixed (1 species) without considering full permutation. The remaining six positions are filled by six people, that is, the answer is1* 6 * C62 * C42 *1/2 = 270.