2019 (CCPC-Final 2019) K. Russian Dolls on the Christmas(dsu one tree)

Posted 2021-05-24 issue是fw

LINK

子树内的问题,每次把子树内的点扔进数组里暴力维护

保留重儿子启发式合并即可

#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e6+10; 
int t,n;
struct edge{
	int to,nxt;
}d[maxn]; int heaed[maxn],cnt=1;
vector<int>vec[maxn];
int dfn[maxn],low[maxn],ID[maxn],id;
int siz[maxn],son[maxn],vis[maxn];
void dfs(int u,int fa)
{
	son[u] = 0; siz[u] = 1; dfn[u] = ++id; ID[id] = u;
	for( auto v:vec[u] )
	{
		if( v==fa )	continue;
		dfs(v,u);
		siz[u] += siz[v];
		if( siz[v] > siz[son[u]] )	son[u] = v;
	}
	low[u] = id;
}
int SON,res,ans[maxn];
void insert(int w,int keep)
{
	if( keep==1 )
	{
		vis[w] = 1;
		if( vis[w-1] && vis[w+1] )	res--;	
		else if( vis[w-1] || vis[w+1] )	return;
		else	res++;
	}
	else
	{
		vis[w] = 0;
		if( vis[w-1] && vis[w+1] )	res++;
		else if( vis[w-1] || vis[w+1] )	return;
		else	res--;
	}
}
void calc(int u,int fa,int keep)
{
	insert( u,keep );
	for(auto v:vec[u] )
	{
		if( v==SON || v==fa )	continue;
		for(int j=dfn[v];j<=low[v];j++)	insert( ID[j],keep);
	}
}
void dsu(int u,int fa,int keep)
{
	for( auto v:vec[u] )
	{
		if( v==fa || v==son[u] )	continue;
		dsu(v,u,0);
	}
	if( son[u] )	dsu(son[u],u,1),SON = son[u];
	calc( u,fa,1 );  
	ans[u] = res; SON = 0;
	if( !keep )		calc(u,fa,0); 
}
int main()
{
	int casenum=0;	cin >> t;
	while( t-- )
	{
		cin >> n ;
		for(int i=1;i<n;i++)
		{
			int l,r; scanf("%d%d",&l,&r);
			vec[l].push_back( r ), vec[r].push_back( l );
		}
		dfs(1,1); 
		dsu(1,1,0);
		printf("Case #%d: ",++casenum);
		for(int i=1;i<=n;i++)	printf("%d%c",ans[i],i==n?'\\n':' ');
		for(int i=1;i<=n;i++)	vec[i].clear();
		id = res = 0;
	}
}