The central problem of permutation and combination is to study the total number of possible situations in a given permutation and combination. Permutation and combination are closely related to classical probability theory.
Extended data:
Addition principle sum sorting counting method for permutation and combination
1. addition principle: There are n ways to do one thing, and finish it. In the first mode, there are m 1 different modes, in the second mode, there are m2 different modes, ... and in the n modes, there are mn different modes, so there are n = M 1+M2+M3+. ...
3. The method of the first method belongs to the set A 1, the method of the second method belongs to the set A2, ..., and the method of the n method belongs to the set An, so the method to accomplish this belongs to the set A 1ua2u...uan.
3. Classification requirements: each method in each category can accomplish this task independently; The specific methods in the two different methods are different from each other (that is, the classification is not heavy); Any method to accomplish this task belongs to a certain category (that is, classification does not leak).
References:
Permutation and combination-Baidu Encyclopedia