欢迎访问~原文出处——博客园-zhouzhendong 去博客园看该题解 题目传送门 - POJ1487 题解概括 给出多个树形结构,由小写字母和数字表示,每个小写字母表示一棵小树.现在,以a为根节点,构建一棵大树,树可能是无限的.现在,一个人从树根往叶子走,直到无法走为止,得到该叶子结点上数值所表示的相应分数,人在分叉的地方走每条路的概率是一样的,求得分期望. 题解 首先通过关系建立方程组. 这个貌似很麻烦,但是很暴力,有码量没有难度. 然后高斯消元解方程. 要注意精度的问题. 解的时候要标记…

[CF446D]DZY Loves Games 题意:一张n个点m条边的无向图,其中某些点是黑点,1号点一定不是黑点,n号点一定是黑点.问从1开始走,每次随机选择一个相邻的点走过去,经过恰好k个黑点到达n的概率. $n\le 500,m\le 500000,k\le 10^9$,黑点个数不超过100. 题解:一眼就知道是高斯消元和矩乘什么的.我们先预处理出f[i][j]表示从第i个黑点开始走到的下一个黑点是j的概率.这个用高斯消元容易搞定.然后上矩乘即可.但是问题在于如果这样做的话我们要做n遍高…

Single-Player Games Time Limit: 1000MS   Memory Limit: 10000K Total Submissions: 1287   Accepted: 362 Description Playing games is the most fun if other people take part. But other players are not always available if you need them, which led to the i…

虽说这题看大家都改得好快啊,但是为什么我感觉这题挺难.(我好菜啊) 所以不管怎么说那群切掉这题的大佬是不会看这篇博客的所以我要开始自嗨了. 这题,明显是树dp啊.只不过出题人想看你发疯,询问二合一了而已. 对于给出了a数组要求b数组的询问,想象一下怎么求. 你先yy一棵树,我懒得画了...父节点叫fa,子节点叫s 那么想一想对于s来说它的答案来自与哪里. 首先是它的子树,设以s为根的子树的a值和为w[s],而子树对它的总贡献是son[s] 那么这样理解:所有子树里的点都需要先走到s的直接儿子们,…

Codeforces 题目传送门 & 洛谷题目传送门 神仙题,%%% 首先考虑所有格子都是陷阱格的情况,那显然就是一个矩阵快速幂,具体来说,设 \(f_{i,j}\) 表示走了 \(i\) 步到达 \(j\) 点的概率,那显然有 \(dp_{i+1,k}\leftarrow dp_{i,j}\times\dfrac{1}{\delta^+(j)}\)(\(j,k\) 之间有边相连),矩阵快速幂优化一下即可,最终答案即为 \(f_{k-1,n}\),时间复杂度 \(n^3\log k\). 接下来…

Revenge of Nim II Problem DescriptionNim is a mathematical game of strategy in which two players take turns removing objects from distinct heaps. On each turn, a player must remove at least one object, and may remove any number of objects provided th…

Zhu and 772002 Problem Description Zhu and 772002 are both good at math. One day, Zhu wants to test the ability of 772002, so he asks 772002 to solve a math problem. But 772002 has a appointment with his girl friend. So 772002 gives this problem to y…

275. To xor or not to xor   The sequence of non-negative integers A1, A2, ..., AN is given. You are to find some subsequence Ai 1, Ai 2, ..., Ai k (1 <= i 1 < i 2 < ... < i k<= N) such, that Ai 1 XOR Ai 2 XOR ... XOR Ai k has a maximum valu…

POJ   1681---Painter's Problem(高斯消元) Description There is a square wall which is made of n*n small square bricks. Some bricks are white while some bricks are yellow. Bob is a painter and he wants to paint all the bricks yellow. But there is something…

原题链接:http://acm.hdu.edu.cn/showproblem.php?pid=4870 原题: Rating Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 654    Accepted Submission(s): 415 Special Judge Problem Description    A little…