Educational Codeforces Round 2 E Lomsat gelral(启发式合并)

本文介绍了一种使用树形动态规划的方法来解决每个子树中支配颜色的问题。通过维护子树中颜色出现的最大次数及其对应的总和,实现启发式合并。适用于需要计算每个节点子树中出现最多次数的颜色或多个并列颜色之和的问题。

摘要生成于 C知道 ,由 DeepSeek-R1 满血版支持, 前往体验 >

思路:维护每个子树颜色最多的数量以及每个颜色拥有的数量,然后启发式合并一波


#include<bits/stdc++.h>
using namespace std;
#define LL long long
const int maxn = 1e5+7;
vector<int>e[maxn];
int n,c[maxn],num[maxn];   //
LL ans[maxn];
map<int,int>cnt[maxn];   //cnt[u][i] 以u的子树有多少种颜色i

void dfs(int u,int fa)
{
	num[u]=1;
	ans[u]=c[u];
    cnt[u][c[u]]=1;
	for(int i = 0;i<e[u].size();i++)
	{
		int v= e[u][i];
		if(v==fa)continue;
		dfs(v,u);
		if(cnt[u].size()<cnt[v].size())
		{
			swap(cnt[u],cnt[v]);
			swap(num[u],num[v]);
			ans[u]=ans[v];
		}
		for(map<int,int>::iterator it = cnt[v].begin();it!=cnt[v].end();it++)
		{
			 cnt[u][it->first]+=it->second;
             if(cnt[u][it->first] > num[u])
			 {
				 ans[u]=it->first;
				 num[u]=cnt[u][it->first];
			 }
			 else if (cnt[u][it->first] == num[u])
			 {
				 ans[u]+=it->first;
			 }
		}
	}
}
int main()
{
    scanf("%d",&n);
	for(int i = 1;i<=n;i++)
		scanf("%d",&c[i]);
	for(int i = 1;i<=n-1;i++)
	{
		int u,v;
		scanf("%d%d",&u,&v);
		e[u].push_back(v);
		e[v].push_back(u);
	}
	dfs(1,-1);

	for(int i = 1;i<=n;i++)
		printf("%lld%c",ans[i],i==n?'\n':' ');
}


E. Lomsat gelral
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output

You are given a rooted tree with root in vertex 1. Each vertex is coloured in some colour.

Let's call colour c dominating in the subtree of vertex v if there are no other colours that appear in the subtree of vertex v more times than colour c. So it's possible that two or more colours will be dominating in the subtree of some vertex.

The subtree of vertex v is the vertex v and all other vertices that contains vertex v in each path to the root.

For each vertex v find the sum of all dominating colours in the subtree of vertex v.

Input

The first line contains integer n (1 ≤ n ≤ 105) — the number of vertices in the tree.

The second line contains n integers ci (1 ≤ ci ≤ n), ci — the colour of the i-th vertex.

Each of the next n - 1 lines contains two integers xj, yj (1 ≤ xj, yj ≤ n) — the edge of the tree. The first vertex is the root of the tree.

Output

Print n integers — the sums of dominating colours for each vertex.

Examples
input
4
1 2 3 4
1 2
2 3
2 4
output
10 9 3 4
input
15
1 2 3 1 2 3 3 1 1 3 2 2 1 2 3
1 2
1 3
1 4
1 14
1 15
2 5
2 6
2 7
3 8
3 9
3 10
4 11
4 12
4 13
output
6 5 4 3 2 3 3 1 1 3 2 2 1 2 3

评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值