解题：ZJOI 2015 幻想乡战略游戏

题面

神**所有点都爆int，我还以为我写出什么大锅了，不开long long见祖宗。。。

动态点分治利用点分树树高不超过log的性质，我们对每个点维护一个子树和，一个点分树子树和，一个点分树上父亲的子树和。修改直接爬点分树，查询在点分树上往答案较小的儿子上跳，如果儿子都不如自己优说明自己就是最优的

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 const int N=,inf=1e9;
 int n,c,T,t1,t2,t3,cnt,Cnt,sizz;
 int p[N],noww[*N],goal[*N],val[*N];
 int siz[N],dep[N],far[N],imp[N],top[N],dis[N];
 int P[N],Noww[*N],Goal[*N],Val[*N];
 int sze[N],maxx[N],vis[N],fer[N];
 long long sum[N],dst[N][];
 void Link(int f,int t,int v)
 {
     noww[++cnt]=p[f],p[f]=cnt;
     goal[cnt]=t,val[cnt]=v;
     noww[++cnt]=p[t],p[t]=cnt;
     goal[cnt]=f,val[cnt]=v;
 }
 void Linka(int f,int t,int v)
 {
     Noww[++Cnt]=P[f],P[f]=Cnt;
     Goal[Cnt]=t,Val[Cnt]=v;
     Noww[++Cnt]=P[t],P[t]=Cnt;
     Goal[Cnt]=f,Val[Cnt]=v;
 }
 void DFS(int nde,int fth,int dth)
 {
     int tmp=;
     siz[nde]=,far[nde]=fth,dep[nde]=dth;
     for(int i=p[nde];i;i=noww[i])
         if(goal[i]!=fth)
         {
             dis[goal[i]]=dis[nde]+val[i];
             DFS(goal[i],nde,dth+);
             siz[nde]+=siz[goal[i]];
             if(siz[goal[i]]>tmp)
                 tmp=siz[goal[i]],imp[nde]=goal[i];
         }
 }
 void Gettop(int nde,int tpp)
 {
     top[nde]=tpp;
     if(imp[nde])
     {
         Gettop(imp[nde],tpp);
         for(int i=p[nde];i;i=noww[i])
             if(goal[i]!=far[nde]&&goal[i]!=imp[nde])
                 Gettop(goal[i],goal[i]);
     }
 }
 int LCA(int x,int y)
 {
     while(top[x]!=top[y])
     {
         if(dep[top[x]]<dep[top[y]])
             swap(x,y); x=far[top[x]];
     }
     return dep[x]<dep[y]?x:y;
 }
 long long Dist(int x,int y)
 {
     int lca=LCA(x,y);
     return dis[x]+dis[y]-*dis[lca];
 }
 void Mark(int nde,int fth)
 {
     sze[nde]=,maxx[nde]=;
     for(int i=p[nde];i;i=noww[i])
         if(goal[i]!=fth&&!vis[goal[i]])
         {
             Mark(goal[i],nde);
             sze[nde]+=sze[goal[i]];
             maxx[nde]=max(maxx[nde],sze[goal[i]]);
         }
     maxx[nde]=max(maxx[nde],sizz-sze[nde]);
     if(maxx[nde]<maxx[c]) c=nde;
 }
 void Create(int nde,int fth)
 {
     vis[nde]=true,fer[nde]=fth;
     for(int i=p[nde];i;i=noww[i])
         if(!vis[goal[i]])
         {
             sizz=sze[goal[i]],maxx[c=]=sze[goal[i]];
             Mark(goal[i],),Linka(nde,c,goal[i]),Create(c,nde);
         }
 }
 void Change(int nde,int tsk)
 {
     sum[nde]+=tsk; int mem=nde;
     while(fer[nde])
     {
         long long dist=Dist(fer[nde],mem)*tsk;
         dst[fer[nde]][]+=dist,dst[nde][]+=dist;
         sum[fer[nde]]+=tsk,nde=fer[nde];
     }
 }
 long long Getans(int nde)
 {
     long long ret=dst[nde][]; int mem=nde;
     while(fer[nde])
     {
         long long dist=Dist(fer[nde],mem);
         ret+=dst[fer[nde]][]-dst[nde][];
         ret+=dist*(sum[fer[nde]]-sum[nde]);
         nde=fer[nde];
     }
     return ret;
 }
 long long Query(int nde)
 {
     long long ret=Getans(nde);
     for(int i=P[nde];i;i=Noww[i])
         if(Getans(Val[i])<ret)
             return Query(Goal[i]);
     return ret;
 }
 int main()
 {
     scanf("%d%d",&n,&T);
     for(int i=;i<n;i++)
         scanf("%d%d%d",&t1,&t2,&t3),Link(t1,t2,t3);
     DFS(,,),Gettop(,);
     sizz=n,maxx[c=]=n,Mark(,);
     int mem=c; Create(c,),c=mem;
     while(T--)
     {
         scanf("%d%d",&t1,&t2);
         Change(t1,t2),printf("%lld\n",Query(c));
     }
     return ;
 }