牛客多校第十场总结
A Rikka with Lowbit
期望的定义，前缀和

J Rikka with Nickname
预处理，字符串
D Rikka with Prefix Sum
组合数学，树状数组
F Rikka with Line Graph
归并排序，dp
H Rikka with Ants
计算几何，斜率转化
E Rikka with Equation
中国剩余定理，容斥原理
G Rikka with Shortest Path
树dp
B Rikka with Burrow-Wheeler Transform
BWT+线段树+归并
I Rikka with Zombies
dp，分类讨论，前缀和
C Rikka with Rotate
Polya 定理，Hash