容斥原理学习笔记

首先得晓得两个很基本的式子

[egin{align*} 若g_n&=sum_{i=0}^n C(n,i)*f_i \ 则f_n&=sum_{i=0}^n (-1)^{n-i}*C(n,i)*g_i end{align*} ]

[egin{align*} 若g_n&=sum_{i>=n} C(i,n)*f_i \ 则f_n&=sum_{i>=n} (-1)^{i-n}*C(i,n)*g_i end{align*} ]