树上数颜色（板子）

Posted 2021-11-12 thusloop

//#pragma GCC optimize(2)
//#pragma GCC optimize(3,"Ofast","inline")
#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define pii pair<int,int>
#define ios ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
const int inf=2e18+100;
const int maxn=2e5+100;
int col[maxn],cnt[maxn];
int mson[maxn],son[maxn];//mson重子节点,son儿子节点数 
int ans[maxn],res;
vector<int>g[maxn];
void dfs(int x,int f)
{
	son[x]=1;
	for(auto it:g[x])
	{
		if(it==f)continue;
		dfs(it,x);
		son[x]+=son[it];
		if(son[it]>son[mson[x]])mson[x]=it;
	}
}
void go(int x,int f,int op)
{
	cnt[col[x]]+=op;
	if(op==1&&cnt[col[x]]==1)res++;
	//if(op==-1&&cnt[col[x]]==0)res--;
	for(auto it:g[x])
	{
		if(it==f)continue;
		go(it,x,op);
	}
}
void dfs2(int x,int f,bool del)
{
	for(auto it:g[x])
	{
		if(it==f||it==mson[x])continue;
		dfs2(it,x,1);
	}
	if(mson[x])dfs2(mson[x],x,0);
	cnt[col[x]]++;
	if(cnt[col[x]]==1)res++;
	for(auto it:g[x])
	{
		if(it==f||it==mson[x])continue;
		go(it,x,1);
	}
	ans[x]=res;
	if(del)
	{
		res=0;//删除轻子节点信息 
		go(x,f,-1);
	}
}
signed main()
{
	IOS 
	int n,m;
	cin>>n;
	for(int i=1;i<n;i++)
	{
		int u,v;
		cin>>u>>v;
		g[u].pb(v);
		g[v].pb(u);
	}
	for(int i=1;i<=n;i++)
	{
		cin>>col[i];
	}
	dfs(1,-1);
	dfs2(1,-1,0);
	cin>>m;
	while(m--)
	{
		int x;
		cin>>x;
		cout<<ans[x]<<"\\n";
	}
}