bzoj 2286: [Sdoi2011消耗战

 #include<cstdio>
 #include<iostream>
 #define M 1000009
 #define N 250009
 #define ll long long
 #define inf 1000000000000000000LL
 #include<algorithm>
 using namespace std;
 int n,head[N],next[M],u[M],cnt,fa[N][],deep[N],m,h[N],dfn[N],TI,cnt1,zhan[N],tot,head1[N];
 int next1[M],u1[M],v[M];
 ll mn[N],f[N];
 void jia(int a1,int a2,int a3)
 {
     cnt++;
     next[cnt]=head[a1];
     head[a1]=cnt;
     u[cnt]=a2;
     v[cnt]=a3;
     return;
 }
 void jia2(int a1,int a2)
 {
     if(a1==a2)
       return;
     cnt1++;
     next1[cnt1]=head1[a1];
     head1[a1]=cnt1;
     u1[cnt1]=a2;
     return;
 }
 void dfs(int a1)
 {
     dfn[a1]=++TI;
     for(int i=;(<<i)<=deep[a1];i++)
       fa[a1][i]=fa[fa[a1][i-]][i-];
     for(int i=head[a1];i;i=next[i])
       if(u[i]!=fa[a1][])
         {
             deep[u[i]]=deep[a1]+;
             fa[u[i]][]=a1;
             mn[u[i]]=min(mn[a1],(ll)v[i]);
             dfs(u[i]);
         }
 }
 bool cmp(int a1,int a2)
 {
     return dfn[a1]<dfn[a2];
 }
 int lca(int a1,int a2)
 {
     if(deep[a1]<deep[a2])
       swap(a1,a2);
     int a3=deep[a1]-deep[a2];
     for(int i=;i<=;i++)
       if(a3&(<<i))
         a1=fa[a1][i];
     for(int i=;i>=;i--)
       if(fa[a1][i]!=fa[a2][i])
         {
             a1=fa[a1][i];
             a2=fa[a2][i];
         }
     if(a1==a2)
       return a1;
     return fa[a1][];
 }
 void dp(int a1)
 {
     ll tmp=;
     f[a1]=mn[a1];
     for(int i=head1[a1];i;i=next1[i])
       {
         dp(u1[i]);
         tmp+=f[u1[i]];
       }
     head1[a1]=;
     if(tmp<f[a1]&&tmp)
       f[a1]=tmp;
     return;
 }
 void solve()
 {
     cnt1=;
     scanf("%d",&h[]);
     for(int i=;i<=h[];i++)
       scanf("%d",&h[i]);
     sort(h+,h+h[]+,cmp);
     int tot=;
     h[++tot]=h[];
     for(int i=;i<=h[];i++)
         if(lca(h[tot],h[i])!=h[tot])h[++tot]=h[i];
     h[]=tot;
     tot=;
     zhan[++tot]=;
     for(int i=;i<=h[];i++)
       {
         int f=lca(h[i],zhan[tot]);
         for(;;)
           {
             if(deep[f]>=deep[zhan[tot-]])
               {
                   jia2(f,zhan[tot]);
                   tot-=;
                   if(zhan[tot]!=f)
                     {
                             tot+=;
                             zhan[tot]=f;
                      }
                   break;
               }
             jia2(zhan[tot-],zhan[tot]);
             tot-=;
           }
         if(h[i]!=zhan[tot])
            {
             tot+=;
               zhan[tot]=h[i];
            }
       }
     for(;tot>;jia2(zhan[tot-],zhan[tot]),tot--);
     dp();
     printf("%lld\n",f[]);
     return;
 }
 int main()
 {
     scanf("%d",&n);
     for(int i=;i<n;i++)
       {
         int a1,a2,a3;
         scanf("%d%d%d",&a1,&a2,&a3);
         jia(a1,a2,a3);
         jia(a2,a1,a3);
       }
     mn[]=inf;
     dfs();
     scanf("%d",&m);
     for(int i=;i<=m;i++)
       solve();
     return ;
 }

显然想到DP，然而DP超时，这个题是构建虚树，然后DP。