题目 Source http://acm.hdu.edu.cn/showproblem.php?pid=5909 Description Byteasar has a tree T with n vertices conveniently labeled with 1,2,...,n. Each vertex of the tree has an integer value vi. The value of a non-empty tree T is equal to v1⊕v2⊕...⊕vn,…

题目链接 hdu5909 题解 设\(f[i][j]\)表示以\(i\)为根的子树,\(i\)一定取,剩余节点必须联通,异或和为\(j\)的方案数 初始化\(f[i][val[i]] = 1\) 枚举儿子\(v\)转移 \[f[i][j] = f[i][j] + \sum\limits_{x \; xor \; y = j} f[i][x] \centerdot f[v][y]\] 发现是一个异或卷积的形式 前面相当于和\(1\)的卷积,后面是和\(f[v]\)的卷积 \(FWT\)即可优化到\…

传送门:http://acm.hdu.edu.cn/showproblem.php?pid=5909 [题解] 设$f_{x,i}$表示以$x$节点的子树中,权值为$i$的子树个数,其中$x$必选. 那么有dp方程:$f_{x,i} = \sum_{y = son[x]} f_{x,i} + \sum_{j \oplus k = i}f_{x, j}f_{y, k}$ 用FWT优化转移即可,复杂度$O(nmlogm)$. # include <stdio.h> # include <st…

[HDU5909]Tree Cutting(FWT) 题面 vjudge 题目大意: 给你一棵\(n\)个节点的树,每个节点都有一个小于\(m\)的权值 定义一棵子树的权值为所有节点的异或和,问权值为\(0..m-1\)的所有子树的个数 题解 考虑\(dp\) 设\(f[i][j]\)表示以\(i\)为根节点的子树中,异或和为\(j\)的子树的个数 很显然,每次合并就是两个\(dp\)值做\(xor\)卷积 那么直接用\(FWT\)优化就行了 #include<iostream> #inclu…

Tree Cutting Problem Description Byteasar has a tree T with n vertices conveniently labeled with 1,2,...,n. Each vertex of the tree has an integer value vi.The value of a non-empty tree T is equal to v1⊕v2⊕...⊕vn, where ⊕ denotes bitwise-xor.Now for…

3391: [Usaco2004 Dec]Tree Cutting网络破坏 Time Limit: 1 Sec  Memory Limit: 128 MBSubmit: 47  Solved: 37[Submit][Status] Description     约翰意识到贝茜建设网络花费了他巨额的经费,就把她解雇了．贝茜很愤怒,打算狠狠报 复．她打算破坏刚建成的约翰的网络．    约翰的网络是树形的,连接着N(1≤N≤10000)个牛棚．她打算切断某一个牛棚的电源,使和这个牛棚相连的所有电缆全…

因为是棵树 , 所以直接 dfs 就好了... ------------------------------------------------------------------------------------- #include<cstdio> #include<cstring> #include<algorithm> #include<iostream>   #define rep( i , n ) for( int i = 0 ; i <…

Tree Cutting Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 262144/131072 K (Java/Others) Problem Description Byteasar has a tree TTT with nnn vertices conveniently labeled with 1,2,...,n1,2,...,n1,2,...,n. Each vertex of the tree has an intege…

3391: [Usaco2004 Dec]Tree Cutting网络破坏 Time Limit: 1 Sec  Memory Limit: 128 MBSubmit: 76  Solved: 59[Submit][Status][Discuss] Description     约翰意识到贝茜建设网络花费了他巨额的经费,就把她解雇了．贝茜很愤怒,打算狠狠报 复．她打算破坏刚建成的约翰的网络．    约翰的网络是树形的,连接着N(1≤N≤10000)个牛棚．她打算切断某一个牛棚的电源,使和这个牛…

hdu 5909 Tree Cutting 题意:一颗无根树,每个点有权值,连通子树的权值为异或和,求异或和为[0,m)的方案数 \(f[i][j]\)表示子树i中经过i的连通子树异或和为j的方案数 转移类似背包,可以用fwt加速 #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> using namespace std; typedef long lon…