Add on a Tree time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Note that this is the first problem of the two similar problems. You can hack this problem only if you solve both problems. You…

Codeforces 280C Game on tree LINK 题目大意:给你一棵树,1号节点是根,每次等概率选择没有被染黑的一个节点染黑其所有子树中的节点,问染黑所有节点的期望次数 #include<bits/stdc++.h> using namespace std; #define N 100010 int n,tot=0,head[N]={0}; struct Edge{int v,nxt;}E[N<<1]; void add(int u,int v){ E[++tot…

题目描述: Game on Tree time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output Momiji has got a rooted tree, consisting of n nodes. The tree nodes are numbered by integers from 1 to n. The root has num…

题目链接:Codeforces 461B Appleman and Tree 题目大意:一棵树,以0节点为根节点,给定每一个节点的父亲节点,以及每一个点的颜色(0表示白色,1表示黑色),切断这棵树的k条边,使得树变成k+1个联通分量.保证每一个联通分量有且仅有1个黑色节点.问有多少种切割方法. 解题思路:树形dp,dp[i][0]和dp[i][1]分别表示子树一下的切割方法中,i节点所在联通块不存在黑节点和已经存在一个黑节点的方案数. #include <cstdio> #include &l…

Codeforces 1129 E.Legendary Tree 解题思路: 这题好厉害,我来复读一下官方题解,顺便补充几句. 首先,可以通过询问 \(n-1​\) 次 \((S=\{1\},T=\{2\dots n\},i),i\in[2,n]​\) ,来得到以 \(1​\) 为根树的所有节点的子树大小. 然后考虑从子树大小最小的节点开始,为每一个节点找它们的儿子,由于每个节点儿子的子树大小,一定小于这个节点的子树大小,所以可以按照子树大小从小到大排序,每个节点的儿子就一定在其前面. 假设已经…

Codeforces Round #781 C. Tree Infection time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output A tree is a connected graph without cycles. A rooted tree has a special vertex called the root. The p…

传送门 首先可以证明一颗树合法的充分必要条件是不存在某个节点的度数为 $2$ 首先它是必要的,考虑任意一条边连接的两点如果存在某一点 $x$ 度数为 $2$ ,那么说明 $x$ 还有连一条边出去,那么连出去的那一条边和当前边的权值就永远一样 然后它是充分的,考虑进行如下操作:首先设当前边连接的两端分别为 $L,R$ ,如果 $L,R$ 只要存在某一个度数为 $1$ 显然合法 然后考虑 $L,R$ 度数不为 $1$ 的情况,那么 $L,R$ 一定分别存在两个儿子连向叶子,设为 $Lx,Ly,Rx,…

On Changing Tree Time Limit: 2000ms Memory Limit: 262144KB This problem will be judged on CodeForces. Original ID: 396C64-bit integer IO format: %I64d      Java class name: (Any)   You are given a rooted tree consisting of n vertices numbered from 1 …

E. Anton and Tree time limit per test: 3 seconds memory limit per test :256 megabytes input:standard input output: standard output Anton is growing a tree in his garden. In case you forgot, the tree is a connected acyclic undirected graph. There are …

题目链接: http://codeforces.com/contest/161/problem/D D. Distance in Tree time limit per test 3 secondsmemory limit per test 512 megabytes 问题描述 A tree is a connected graph that doesn't contain any cycles. The distance between two vertices of a tree is th…