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……

高程复习 C++与C的关系 C++包含了C的所有成分 添加了： 更好的支持过程式编程，提高与类型相关的安全性 支持面向对象 支持泛型 带参数的宏定义的缺点： 需要加上很多括号 会出现重复计算 (e.g. ```max(x+1,y*2)```) 不进行类型检查和转换 不利于一些工具对程序……

This proof is due to Arturo Magidin. In category theory, as we don't consider the 'internal structure' of objects, many properties of maps are defined in an abstract way using interaction with other morphisms. 'Epimorphism' is such an analog of sur……

如题，笔者作为队伍中的编程手，将在此分享自己的准备历程。队伍准备打MothorCup和电工杯，最终在9月份参加国赛。 3.15 线性规划模型: from scipy import optimize import numpy as np c = np.array([-4,-3]) # 默认求最小值 所以求最大值时需要加 - A = np.array([……