Solved! Difficulty: Div2D 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 - M……

题目背景: 来自中等数学2021.4数学奥林匹克问题, 可能是这个栏目下有史以来最水的题, 以下解法非标答(因为没买No.5), 或许略显繁琐 题目: 设实数x_i(i=1,2,..,n)使得\sum_{i=1}^{n}x_i=0且\sum_{i=1}^{n}x_i^2=n(n-1). 证明: |\sum_{i=1}^nx_i^3|\leq n(n-1)(n-2) ……

题目背景: 在t教师课后, w同学提出此问题. 在现场的我由于过于弱智, 没能及时想出思路. 在回家途中准备展开时, 却无意中发现了"绝妙"的突破口. :i 题目: 求\prod_{i=1}^{n}(1+cos\frac{2i\pi}{n}) 先想再看提示哦 提示: 切比雪夫多项式 ……

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 ……

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

From Hexo Useful 思考题!! Replace Hikari is a cute white dragon girl. She is helping Ninetail - a fox girl, her master - correct composition.The original composition is a string S and the corrected one is another string T. Hikari claimed that……

From Hexo String 思考题!! Boggle Constructor Ninetail is a clever fox girl. She loves to play Boggle! the rules are simple: Each player searches for words that can be constructed from the letters of sequentially adjacent cubes, where "adjace……

By HDD from Hexo 时隔多月, CB终于归来. 这次的题目虽然不难, 但解答过程可谓是一波三折: A在告诉我题目后, 我自然地尝试用复数解. 可惜由于我太过弱智, 将积的模记成了模相乘再开根, 导致与正确题解失之交臂, 并报告了A复数行不通. A随后告诉我B用复数解决, 我……

By MonkeyKing from Hexo 所谓algorithms unweekly， 就是开心的时候就写点的有关的algorithms的blog, 如果你喜欢weekly的algorithms, 请移步这里Algorithms weekly by Petr。 那么你现在看到的就是第一篇algorithms unweekly，这篇文章讲的是笔者2020年第四季……

由于笔者太弱智,这道题想了两天无任何思路.但在上完夏建国课后,突然思如泉涌,在10分钟内完成,金与大家分享一下我的歪门邪道 题面 已知x_i>0(i=1,2,...,n),x_1+x_2+...+x_n\geq x_1x_2...x_n(n\geq2),且1\leq\alpha\leq n 证明:\frac{x_1^\alpha+x_2^\alpha+...+x_n^\a……