(A, B, C)

( 1、 1、5),( 1、5、 1),(5、 1、 1),

( 1、2、4),( 1、4、2),(2、 1、4),(2、4、 1),(4、 1、2),(4、2、 1),

( 1、3、3),(3、 1、3),(3、3、 1)。

Common methods of permutation and combination

1, binding method

Questions with the characteristics of "together" and "adjacent" often appear in the combination of mathematical operations. At this time, we consider the binding method (also called packaging method by some teachers), that is, the elements that are "together" are "bound". The specific steps are: first sort within the binding, and then sort between the binding body and other elements.

2. Interpolation

In the problem of permutation and combination, several elements are often required to be "not together" and "not adjacent" when sorting. At this time, the interpolation method can be considered.