# 跃迁引擎启动

rank solved A B C D E F G H I J K L
74 7 O O ! O O O ! . . O . O

Solved by XLor.

Solved by XLor.

# C

UnSolved by Forsaken.

Solved by Henry.

# E

Solved by Forsaken.

$f(2k)$为用$cnt_{0}$种球放$2k$个盒子，且每种球个数为偶数的方案数

$g(x)^m=\frac{\sum_{i=0}^{m}C(m,i)e^{(m-2i)x}}{2^m}$

$ans=\sum_{k=0}^{\lfloor \frac{n}{2}\rfloor} C(n,2k)cnt_{1}^ninvcnt_1^{2k}\frac{\sum_{i=0}^{cnt_0}C(cnt_0,i)(cnt_0-2i)^{2k}}{2^{cnt_0}}$

$ans= \frac {cnt_{1}^{n}}{2^{cnt_0}}\sum_{i=0}^{cnt_0}C(cnt_0,i)\sum_{k=0}^{\lfloor \frac{n}{2}\rfloor}C(n,2k)(invcnt_1(cnt_0-2i))^{2k}$

$ans=\frac {cnt_{1}^{n}}{2^{cnt_0}}\sum_{i=0}^{cnt_0}C(cnt_0,i)\frac{(1+invcnt_1(cnt_0-2i))^n+(1-invcnt_1(cnt_0-2i))^n}{2}$

Solved by Henry.

# G

UnSolved by XLor.

Solved by Henry.

Solved by Henry.