Note: this problem is drafted on 2019/7/30 by XGN and not released. It's now released on 2022/1/2 by Zzzyt under his permission. Statement Yuqi has an rooted indexed tree T of N nodes indexed from 1 to N. The node 1 is the root. Now on each node th……

思考题 so easy just to prove I am not dead ESL Wulpit is a divine fox spirit. She is learning Chinese. So she doesn't understand English. One day she received an English string S of n lower case characters. XGN told her how her name would be like i……

0.声明 算法第一 常优第二 C++是算法的载体，为算法服务。本系列的目的不在于推崇常优，而是解除OIer对常数的顾虑而专注于算法。 环境 编译参数 语言标准 优化等级 NOIP(2020) i7-8700K @3.70GHz 32GNOI Linux 1.4.1gcc 4.8.4 -lm c++11 O0 NOIP(2021+)……

0.声明 算法第一 常优第二 C++是算法的载体，为算法服务。本系列的目的不在于推崇常优，而是解除OIer对常数的顾虑而专注于算法。 环境 编译参数 语言标准 优化等级 NOIP(2020) i7-8700K @3.70GHz 32GNOI Linux 1.4.1gcc 4.8.4 -lm c++11 O0 NOIP(2021+)……

思考题 with git Version Control You are given a DAG with N nodes and M direcitonal edges. Node 1 has 0 in degree. We define a node i is required for node j if i is in any path from 1 to j. You are given Q queries, for each query you are given A and……

Long time no see 思考题 Tree Traversing Hikari has a tree of N nodes. The node #1 is the root. Initially she is at node 1. She can do one of the following three operations: - Move to any adjacant node with cost 1 - Mark current node as temporary st……

chemistry 思考题 Hydrocarbon Ninetail is building a tree. She has N nodes and she will assign a value from 0 to 3 to each node. All nodes with the same value are indistinguishable. Then she will connect the N nodes with N-1 edges so that they form ……

MonkeyKing got into Jiangsu Province Team of OI!!! Congratulations!!

OBCYSIO Ep.41 to 43 is hosted on XGN's blog. As I am lazy to copy, please read them here

From Hexo Also available on XGN Blog 大家好，我是每年都去省选摸鱼的XGN，今年一如既往的抱着旅游的心态去打JSOI，没想到竟然在我们学校……（计划泡汤 所以只能讲讲考场那些事了。 Day 0 周五下午试机还要上cr的选修课（也在机房）。于是就被ls老师叫去当无价劳……