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  • crimboi[15] 序数拓扑(?)
    题&解

    crimboi[15] 序数拓扑(?)

    题目背景 本题竟然与xgn目前正在学习的序数有关, 真是可喜可贺!(crim boi在thu里有包含序数的课程吗?) 题面 If you don't remember what a topology is, please refer to this passage. Preliminary: Open sets in \mathbb R are just union (can be infinite) of som……
    HDD 2023年11月1日
  • Green Boy Can't You Solve It Out? Ep. 2
    OBCYSIO

    Green Boy Can't You Solve It Out? Ep. 2

    Solved! Difficulty: Div2B 1 problem for div3 participants. Beautiful Dice Painting When Epis is bored, she will draw dices. The canvas contains n*n dots. Initially they are all white. You need to paint exactly v dots black so that the final c……
    XGN 2023年10月22日
  • Crimboi [14] 开门红(?)
    题&解

    Crimboi [14] 开门红(?)

    题目背景 Rudin Real and Complex Analysis第一题, 真是开门红. 题面 We call a pairing (X,\mathfrak{M}) \sigma-algebra if \mathfrak{M} is a subset of P(X) satisfying the three properties below: (1) X\in\mathfrak{M} (2) If A\in\mathfrak{M}, A^c\in\mathf……
    HDD 2023年10月11日
  • Orange Boy Can You Solve It Out? Ep. 57
    OBCYSIO

    Orange Boy Can You Solve It Out? Ep. 57

    trivial 思考题 I am Banach This is a classic problem by Banach nearly without any change. There are N boys and M girls. Each boy loves a single girl and each girl loves a single boy. Your task is to divide the boys into two groups A_0 and A_1 and t……
    XGN 2023年10月7日
  • Announcement on Solutions for Orange Boy Can You Solve It Out
    OBCYSIO

    Announcement on Solutions for Orange Boy Can You Solve It Out

    Starting from today, we will try to write tutorials and rate difficulties for already solved Orange Boy Can You Solve It Out?(OBCYSIO) problems and separate them from unsolved/unsolvable ones. There's a new category called Solved OBCYSIO and you ca……
    XGN 2023年10月6日
  • Orange Boy Can You Solve It Out? Ep. 56
    OBCYSIO

    Orange Boy Can You Solve It Out? Ep. 56

    思考题 during OI recovery Rubbish Problem Maybe you have heard of the evil problem Hilbert's Hedge Maze and here's another very fun problem! You have n items arranged in rows. Each row contains r items and the items are arranged from left to right,……
    XGN 2023年10月6日
  • Crimson boi can u water it [13] 几把水题
    题&解

    Crimson boi can u water it [13] 几把水题

    题目背景 南大几把选拔中最水的题(T3), 适合出在初中竞赛里. 另外这期写解答方便以后想考南大几把的学生😇, 篇幅太长除了题面不写中文了. 不过题面也是pmt提供的, 不一定完全准确. 题面 记排列P的置换环数量为c(P),排列P,Q的复合记为P\oplus Q,已知长度为n的排列f_1,f……
    HDD 2023年9月6日
  • 上海游记(zky&wzz)
    文学

    上海游记(zky&wzz)

    (提醒:本游记体量较大,字数超过10000,图片数量超过100,可以考虑在WiFi环境下阅读)   “晕眩于它的华美,在放纵中失魂落魄。于是,欢乐、惊奇、悲伤,我感到一种无可名状的激动”,上世纪二十年代,日本作家村松梢风把上海称作“魔都”,而一个世纪之后的今天,虽然……
    ZhukyRLG 2023年8月17日
  • 日行紀要(XGN)
    日记

    日行紀要(XGN)

    概述 本文为XGN(后文称笔者)与其母(后文称母)于令和五年八月六日到十四日的日本国游记,在HHS博客上发表,XGN博客上转录。 「日行紀要」(にこうきよう)? 在笔者之前,已经有一篇翔实而又生动的游记——日本国游记 笔者不及Z氏的文笔和才华,本文也只是简单概述所……
    XGN 2023年8月15日
  • 湖州游记(zky&xgn)
    文学

    湖州游记(zky&xgn)

      我喜欢七月的阳光,虽然炽烈炫目,却让万物都在盛夏绽放出最旺盛的生命;我喜欢七月的温度,即使热浪滚滚,也能在穿过时光与美好的时候感受着酣畅淋漓的畅快。可是也许,我喜欢七月的这一切,更是因为在这个季节,我们可以暂且抛去身后的忙碌,来一场说走就走的旅行……
    ZhukyRLG 2023年7月26日