Description
Solution
在虚树上跑DP即可
Code
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstring>
#define ll long long
#define N 250010
using namespace std;
const ll Inf=1ll<<60;
struct info{int to,nex;ll w;}vir[N*2],e[N*2];
int n,m,tot,head[N],dfn[N],cnt;
int _log,f[N][20],dep[N];
int q[N],sta[N],top;
ll dis[N],dp[N];
inline int read(){
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
inline void Link(int u,int v,int w){
e[++tot].to=v;e[tot].w=w;e[tot].nex=head[u];head[u]=tot;
}
inline void Link_vir(int u,int v){
if(u==v) return;
vir[++tot].to=v;vir[tot].nex=head[u];head[u]=tot;
}
void dfs(int u, int fa){
dfn[u]=++cnt;
for (int j=1;j<=_log;++j) f[u][j]=f[f[u][j-1]][j-1];
for(int i=head[u];i;i=e[i].nex) {
int v=e[i].to;
if (v==fa) continue;
f[v][0]=u;
dis[v]=min(dis[u],e[i].w);
dep[v]=dep[u]+1;
dfs(v,u);
}
}
int LCA(int u,int v){
if(dep[u]>dep[v]) swap(u,v);
int d=dep[v]-dep[u];
for(int i=0;i<=_log;++i)
if(d&(1<<i)) v=f[v][i];
if(u==v) return v;
for(int i=_log;i>=0;--i)
if(f[u][i]!=f[v][i]){
u=f[u][i];
v=f[v][i];
}
return f[u][0];
}
void DP(int x){
ll tmp=0;dp[x]=dis[x];
for(int i=head[x];i;i=vir[i].nex){
int v=vir[i].to;
DP(v);
tmp+=dp[v];
}
head[x]=0;
if(!tmp) dp[x]=dis[x];
else if(tmp<dp[x]) dp[x]=tmp;
}
bool cmp(int a,int b){return dfn[a]<dfn[b];}
void solve(){
m=read();tot=0;
for(int i=1;i<=m;++i) q[i]=read();
sort(q+1,q+m+1,cmp);
cnt=1;
for(int i=2;i<=m;++i) if(LCA(q[i],q[cnt])!=q[cnt]) q[++cnt]=q[i];
sta[top=1]=1;
for(int i=1;i<=cnt;++i){
int grand=LCA(q[i],sta[top]);
while(1){
if(dep[sta[top-1]]<=dep[grand]){
Link_vir(grand,sta[top]); top--;
if(sta[top]!=grand) sta[++top]=grand;
break;
}
Link_vir(sta[top-1],sta[top]); top--;
}
if(sta[top]!=q[i]) sta[++top]=q[i];
}
top--;
while(top) Link_vir(sta[top],sta[top+1]),top--;
DP(1);
printf("%lld
",dp[1]);
}
int main(){
n=read();_log=log(n)/log(2);
for(int i=1;i<n;++i){
int u=read(),v=read(),w=read();
Link(u,v,w);
Link(v,u,w);
}
dis[1]=Inf;dfs(1,0);
memset(head,0,sizeof(head));
int k=read();while(k--) solve();
return 0;
}