此文作讲解的不是数理逻辑, 而是测试逻辑中一个重要定理---超限归纳在拓扑的一个基本定理上的应用(其实还顺带介绍了不少拓扑). 当然, 在本篇的之后可能会讲到佐恩引理, 那么这些用超限归纳解题的过程都能被简化, 这也是大多数教科书所用的做法. 不过归根结底本文目的……

思考题 which is an adaptation from a popular problem. The source problem is very popular. IDK if this adaptation has been made or not. Adaptation There are N people indexed from 1 to N in a room. Each of them is given a hat of a random color. The t……

Finally some geometry! Maybe very easy though. Currently I am undergoing the College Entrance Exam(GK) so I don't have many ideas for Competitive Programming problems. This problem is inspired by some math problem in GK Simulation. Of course, this ……

思考题 of Div2B-C Elevator Welcome back to OBCYSIO! Orange Boy has been promoted to LGM boy so this series is in an awkward situation. This problem is very easy. Consider an elevator with a max speed of v_m m/s and an acceleration of a m/s^2. When ……

After four months of development and nearly six months of Koto and TestSTG 5 development, here is the latest installment of ZJSTG -- ZJSTG2!! Probably the biggest(only) game project in 2022 Introduction ZJSTG2 is a Touhou-style bullet-hell shooting……

anniversary 思考题 Very Easy Problem Wow! OBCYSIO has reached 50 episodes! Let's celebrate using a very popular and easy problem. Hikari and Ninetail are playing a game on an undirected graph of N nodes and M edges. They move in turns, with Hikari ……

Solved! Difficulty: Div2D-Div2E 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 n……

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……

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……

What's New Changed Recipes Added 6 New Items Added boss Momiji Download and Doc Here