bzoj3743: [Coci2015]Kamp

首先树dp求出一个点的答案

然后再一遍dfs换根（是叫做换根吗..

详见代码

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#define ll long long
#define N 500005
#define M 1000006

using namespace std;
inline int read(){
	int ret=0;char ch=getchar();
	while (ch<'0'||ch>'9') ch=getchar();
	while ('0'<=ch&&ch<='9'){
		ret=ret*10-48+ch;
		ch=getchar();
	}
	return ret;
}

struct edge{
	int adj,next,len;
	edge(){}
	edge(int _adj,int _next,int _len):adj(_adj),next(_next),len(_len){}
} e[M];
int n,g[N],m;
void AddEdge(int w,int u,int v){
	e[++m]=edge(v,g[u],w);g[u]=m;
	e[++m]=edge(u,g[v],w);g[v]=m;
}

ll f[N],h[N],t[N],t0[N];
ll f0[N],h0[N];
int size[N],l[N];
int size0[N];
bool vis[N];
void dfs(int u){
	vis[u]=1;
	f[u]=l[u];h[u]=2*l[u];t[u]=0;t0[u]=0;
	for (int i=g[u];i;i=e[i].next){
		int v=e[i].adj;
		if (vis[v]) continue;
		l[v]=e[i].len;
		dfs(v);
		f[u]+=h[v];
		h[u]+=h[v];
		t0[u]=max(t0[u],h[v]-f[v]);
		if (t0[u]>t[u]) swap(t0[u],t[u]);
		size[u]+=size[v];
	}
	if (!size[u]) f[u]=h[u]=0;
	else f[u]-=t[u];
	vis[u]=0;
}

ll ans[N];
void solve(int u){
	vis[u]=1;
	
	f[u]=l[u];h[u]=2*l[u];t[u]=0;t0[u]=0;
	for (int i=g[u];i;i=e[i].next){
		int v=e[i].adj;
		l[v]=e[i].len;
		f[u]+=h[v];
		h[u]+=h[v];
		t0[u]=max(t0[u],h[v]-f[v]);
		if (t0[u]>t[u]) swap(t0[u],t[u]);
		size[u]+=size[v];
	}
	if (!size[u]) f[u]=h[u]=0;
	else f[u]-=t[u];
	
	ans[u]=f[u];
	f0[u]=f[u];h0[u]=h[u];
	size0[u]=size[u];
	for (int i=g[u];i;i=e[i].next){
		int v=e[i].adj;
		if (vis[v]) continue;
		swap(l[u],l[v]);
		if ((size[u]-=size[v])){
			h[u]+=(ll)2*l[u]-h[v];
			f[u]+=(ll)l[u]-h[v];
			if (h[v]-f[v]==t[u]) f[u]+=t[u]-t0[u];
		}
		else f[u]=h[u]=0;
		
		solve(v);
		
		f[u]=f0[u];h[u]=h0[u];
		size[u]=size0[u];
		swap(l[u],l[v]);
	}
	vis[u]=0;
}

int main(){
	n=read();int men=read();
	for (int i=1;i<n;++i) AddEdge(read(),read(),read());
	memset(size,0,sizeof(size));
	while (men--) ++size[read()];
	memset(vis,0,sizeof(vis));
	l[1]=0;
	dfs(1);
	solve(1);
	for (int i=1;i<=n;++i) printf("%lld\n",ans[i]);
	return 0;
}