杭电多校第四场总结

Problem A. Integers Exhibition

开场看这一题发现不会写,然后听dls说是原题，桑心

Problem B. Harvest of Apples

莫队+分块的全场题，不会写桑心，有空补题

Problem C. Problems on a Tree

用并查集维护两种连通块 —— Easy + Medium 题的连通块，维护大小；Easy 题的连通块，维护大小以及与此连通块只隔一个 Hard 题的Easy + Medium 连通块大小之和即可。（by题解）

Problem D. Nothing is Impossible

垃圾，垃圾，浪费了我好几发罚时

Problem E. Matrix from Arrays

发现2L*2L重复出现这就是水题了
代码
Matrix from Arrays

Problem F. Travel Through Time

可持久化 Treap

G. Depth-First Search

深搜+预处理+字典序

Problem H. Eat Cards, Have Fun

这个优化是真的不会。。

Problem I. Delightful Formulas

莫比乌斯反演+伯努利数+NTT

J. Let Sudoku Rotate

搜索+剪枝

Problem K. Expression in Memories

水题

Problem L. Graph Theory Homework

水题