CF1385F Removing Leaves（贪心）

补题。
由最深的节点开始贪心即可。
代码参考：
code
代码如下：

#include<bits/stdc++.h>
using namespace std;
#define MAXN 200010
int head[MAXN],cnt,deg[MAXN],leaves[MAXN];
struct node{
    
    
	int to,from;
}edge[MAXN<<1];
set<int>s[MAXN];
void add(int u,int v)
{
    
    
	cnt++;
	edge[cnt].to = v;
	edge[cnt].from = head[u];
	head[u] = cnt;
}
struct data{
    
    
	int id,leave;
	bool operator <(const data &x)const
	{
    
    
		return leave<x.leave;
	}
};
priority_queue<data>q;
void dfs(int x,int fa)
{
    
    
	if(deg[fa]==1)leaves[x] = 1,s[x].erase(fa);
	for(int i = head[x];i;i = edge[i].from)
	{
    
    
		int to = edge[i].to;
		if(to==fa)continue;
		if(deg[to]==1)s[x].erase(to),leaves[x]++;
		dfs(to,x);
	}
}
int main()
{
    
    
	int t;
	cin>>t;
	while(t--)
	{
    
    
		int n,k,ans=0;
		cin>>n>>k;
		for(int i=1;i<n;i++)
		{
    
    
			int u,v;
			scanf("%d%d",&u,&v);
			add(u,v);
			add(v,u);
			deg[v]++,deg[u]++;
			s[u].insert(v);s[v].insert(u);
		}
		
		if(k==1)
		{
    
    
			printf("%d\n",n-1);
			for(int i=1;i<=n;i++) s[i].clear(),head[i]=leaves[i]=deg[i]=0;
			cnt = 0;
			continue;
		}else
		{
    
    
			dfs(1,-1);
			for(int i=1;i<=n;i++)q.push({
    
    i,leaves[i]});
			while(!q.empty())
			{
    
    
				if(leaves[q.top().id]!=q.top().leave){
    
    
					q.pop();continue;
				}
				int to = q.top().id;
				q.pop();
				if(leaves[to]<k)break;
				while(leaves[to]>=k) leaves[to]-=k,deg[to]-=k,ans++;
				if(!leaves[to]&&deg[to]==1)
				{
    
    
					int p = *s[to].begin();
					leaves[p]++;
					s[p].erase(to);
					if(leaves[p]>=k)q.push({
    
    p,leaves[p]});
				}
			}
			for(int i=1;i<=n;i++) s[i].clear(),head[i]=leaves[i]=deg[i]=0;
			cnt = 0;
			while(!q.empty()) q.pop();
			printf("%d\n",ans);
		}
	}
}