Mathematical permutation and combination problem: four policemen are assigned to three different task forces, and each group is assigned at least one person. How many distribution methods are there?

The first one is right.

The second mistake is that the algorithm using partition method should be sorted before use.

That is, a (4,4) xc (3,2) =12x3 = 72.

72÷2=36 (the "2" here refers to the sorting within the group, for example, BC and CB are actually the same)

But the division before sorting ignores the possibility that two non-adjacent policemen are assigned to the same group.

A B C D means four policemen.

a record

400 BC

AB C D

These are three possibilities of using the partition method.

But there are three possibilities.

AC B D

A.D. BC

A BD C