# 容斥原理表示形式(Representation of inclusion exclusion principle)-其他

## 容斥原理表示形式(Representation of inclusion exclusion principle)

————————

The inclusion exclusion principle is a principle for most people, because this fact is too obvious. When you think about it, the number of elements satisfying a certain condition – the number of elements satisfying a certain two conditions + the number of elements satisfying a certain three conditions is obviously right. So most people take it as a principle, and then they are tortured to death by the person who made the question of cancer.

So this thing needs to be proved. In fact, the inclusion exclusion principle is a kind of inversion. Because you use the number of schemes that meet at least some conditions to deduce the number of schemes that just meet some conditions. Let f (STA) = the number of schemes that at least satisfy the sta condition let g (STA) = the number of schemes that just satisfy the sta condition) if it is at least, then f (STA) = sigma g (ISTA) (ISTA & sta = STA) then G (empty) = f (empty) – f (1) – f (2) – f (3)… + F (1,2) + F (2,3)… This is obviously more, right…… Corresponding g (STA) = sigma ((-1) |tmp| * f (STA | TMP), TMP & sta = 0)