D. Tree and Queries

Posted 2021-10-26 thusloop

Tree and Queries
题意：树上每个节点一个颜色，m个询问，求v节点的子树中颜色出现次数大于等于k的颜色个数

//#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;
vector<int>g[maxn];
vector<pii>v[maxn];
int col[maxn],cnt[maxn],res[maxn],son[maxn],mson[maxn],ans[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)res[cnt[col[x]]]++;
	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]]++;
	res[cnt[col[x]]]++;
	for(auto it:g[x])
	{
		if(it==f||it==mson[x])continue;
		go(it,x,1);
	}
	for(auto it:v[x])
	{
		ans[it.se]=res[it.fi];
	}
	if(del)
	{
		for(int i=1;i<=son[x];i++)res[i]=0;
		go(x,f,-1);
	}

}
signed main()
{
	IOS
	int n,m;
	cin>>n>>m;
	for(int i=1; i<=n; i++)
	{
		cin>>col[i];
	}
	for(int i=1; i<n; i++)
	{
		int x,y;
		cin>>x>>y;
		g[x].pb(y);
		g[y].pb(x);
	}
	for(int i=1; i<=m; i++)
	{
		int x,y;
		cin>>x>>y;
		v[x].pb({y,i});
	}
	dfs(1,-1);
	dfs2(1,-1,0);
	for(int i=1;i<=m;i++)
	{
		cout<<ans[i]<<"\\n";
	}
}