This is a joke Introduction Many new programmers are often confused about a very important concept in programming: the variable lifespan. For example, one could not understand why the variable "a" is "not defined" when it's clearly there: int x=3; ……

ref 起因： 在阅读ics-pa代码macro.h中发现这样一个需求：如何在宏中测试特定宏是否被定义 #define str_temp(x) #x #define str(x) str_temp(x) // strlen() for string constant #define STRLEN(CONST_STR) (sizeof(CONST_STR) - 1) // calculate the length of an……

背景 笔者最近在参加某校在线平台前端的开发，收到了这样的要求： 将服务器传输过来的文件尽可能（图片/PDF）在网页中就显示下来，这样就不用下载了！ 笔者劈里啪啦敲下了如下代码（由于渲染问题，美元符号已替换为人民币符号！！！）： var xhr = new XMLHttpReq……

思考题 featuring Hikari again! Guess the string Hikari and her master Ninetail are playing a game. Hikari thinks of a string S with lower-case letters, and Ninetail asks her to make q modifications one by one. Each modification can only be one of t……

（提醒：本游记体量较大，字数超过21500，图片数量超过100，可以考虑在WiFi环境下阅读）   “慢下来，一倍速生活” ——大理市公益广告标语   在眼前一闪而过的文字，是身处大城市遥不可及的幻想，或许只有一片无比纯净而美丽的山水与天地，才能承载得住这样温暖又令人动……

Dieudonne的题, 真实难度不好说, 回顾一下发现其实挺简单的. 题面 Let E be a Hilbert space, F a dense linear subspace of E, distinct from E. (For example E space of l^2 sum of a suitable countable linear independent set and F space of finite sum of thi……

It's a well known fact that Euclidean domains are principal ideal domain by taking the element in a certain ideal with smallest \varphi value. Yet the converse is false, and one counterexample just lies among our familiar algebraic integer rings, \……

题目背景 为证一个非零吃大师 题面 Assuming AC, prove that for a integral domain R, if any nonzero prime ideal P contains a nonzero prime (p), R is UFD. 先想再看提示哦 提示 Let S be the set of elements that are prime factori……

This proof is due to Choudum. A sequence of nonnegative integers (d_1,...,d_n) is called graphic if there is a simple graph G with V(G)=\lbrace v_1,...,v_n\rbrace and d(v_i)=d_i. It's very easy to show that if a nonincreasing sequence, i.e. d_1\ge ……

飞机上半昏迷状态下以为无法调整, 暴力算出来的搞笑解答. 非常具有统计色彩 (nod) 题面 A simple graph G is called complete k-partite if there's a partion of V(G): A_1,..., A_k s.t. for all i there's no edge with both vertices in A_i , and for any v\in A……