OGF - Cayley Formula Question Statement Prove # of trees on [n] = n^{n-2} Solution f:(1,2,3,...,n)\to(1,2,3,...,n) f(1)=1,f(n)=n Functional Digraph(directed graph) D V(D)=[n] 编者注：V为节点集合 (i,j)\in E(D) if f(i)=j 注：E为边集合 Example | ……

$\mathcal A$ is a collection of combinatorial objects. => $\mathcal A$ and $\mathcal B$ are combinatorically isomorphic if there exist a size-preserving bijection between $\mathcal A$ and $\mathcal B$ Q1 Prove that number of Dyck Paths D_{n-1} equa……

思考题 of math again Slime Legend II In the world of fantasy, there lives N+1 types of monsters indexed from 0 to N. Each monster can be represented by an integer pow_i - their power. And specially, type 0 is SLIME. Slime has a special ability to "……

欢迎来到Hell Hole Studios Blog! 这是一个由HHS成员共同维护的blog网站，主要内容包括游戏、技术、数学、信息竞赛和旅游日记，主要blog语言有中文、英文（备注：点击标签来查看同标签内容）。下面的链接可能会帮助到您更好的浏览本站。 Welcome to the Hell Hole Stu……

Today is the first day of MUTC!!! On this site there will be diary about our team (team0248). Good luck! MUTC is a series of OI contests held every year usually 10 contests in a row.

In a recent Codeforces Contest Codeforces Global Round 4, the Orange Boy MonkeyKing got a T-shirt by getting rank 449. BEST RATING CHANGE

You are given something, what is it? You don't know, but you are curious about it. You want to know what it is, but you can't. It made you unpleasant, you are somewhat angry. 当你的野心还撑不起你的才华时，就应该静下心来评论一下。 Formally,you are g……

思考题 that is quite easy FACT ZJS likes to show off his wonderful calculator. His calculator can do FACT operation which means can divide an integer to some primes' products. For example, Fact(30) will display 2\times3\times5 which is a string of ……

Hi, for everyone watching this. If you are in China, you may know that it is the Great Summer Holiday(Jul.1~Aug.31)! During the summer holiday, we will do updates and new stuffs. Here's the plan: Note:We are not doing this full-time. We have lesson……

思考题 that is easier than #14 Sort and Sort and Sort and Sort You are given an integer array A of length N. And you are given Q queries. For each query, you are given Li and Ri. You need to find out the sum of products of adjcent numbers in the so……