XJOI网上同步训练DAY3 T2

考试的时候已经想出来怎么做了，但是没有时间打了T_T

思路:我们考虑将询问以lim排序，然后树链剖分，把边作为线段树的节点，然后随着询问lim的增大，改变线段树中节点的信息，然后每次询问我们用树链剖分询问，复杂度是O(nlogn）,又get一种新的树链剖分打法

 #include<cstdio>
 #include<cmath>
 #include<iostream>
 #include<algorithm>
 #include<cstring>
 struct node{
     int x,y,lim,id;
 }q[];
 int V[],dep[],t[],dfn[],num,n,m;
 struct Data{
     int l,r,s,v;
     Data(){}
     Data(int a,int b,int c,int d):l(a),r(b),s(c),v(d){}
 }s1[],s2[];
 Data operator +(Data a,Data b){
         Data ret(a.l,b.r,a.s+b.s,a.v+b.v);
         if (a.r&&b.l) ret.v=a.v+b.v-V[a.r]-V[b.l]+V[a.r+b.l];
         if (b.l==b.s) ret.r=a.r+b.s;
         if (a.l==a.s) ret.l=b.l+a.s;
         return ret;
 }
 int tot,go[],next[],first[];
 int size[],son[],top[],fa[];
 int ans[],val[];
 int read(){
     int t=,f=;char ch=getchar();
     while (ch<''||ch>'') {if (ch=='-') f=-;ch=getchar();}
     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}
     return t*f;
 }
 void insert(int x,int y,int z){
     tot++;
     go[tot]=y;
     next[tot]=first[x];
     first[x]=tot;
     val[tot]=z;
 }
 void add(int x,int y,int z){
     insert(x,y,z);insert(y,x,z);
 }
 bool cmp(node a,node b){
     return a.lim<b.lim;
 }
 bool cmp1(int x,int y){
     return val[x]<val[y];
 }
 void build(int k,int l,int r){
     if (l==r){
         s1[k]=s2[k]=Data(,,,V[]);
         return;
     }
     int mid=(l+r)/;
     build(k*,l,mid);
     build(k*+,mid+,r);
     s1[k]=s1[k*]+s1[k*+];
     s2[k]=s2[k*+]+s2[k*];
 }
 void dfs1(int x,int f){
     size[x]=;
     for (int i=first[x];i;i=next[i]){
         int pur=go[i];
         if (pur!=f){
             dep[pur]=dep[x]+;
             t[++t[]]=i;
             dfs1(pur,x);
             size[x]+=size[pur];
             if (size[pur]>size[son[x]]) son[x]=pur;
         }
     }
 }
 void dfs2(int x,int f){
     dfn[x]=++num;
     if (son[x]) top[son[x]]=top[x],dfs2(son[x],x);
     for (int i=first[x];i;i=next[i]){
         int pur=go[i];
         if (pur==f||pur==son[x]) continue;
         top[pur]=pur;
         fa[pur]=x;
         dfs2(pur,x);
     }
 }
 void modify(int k,int l,int r,int pos){
     if (l==r){
         s1[k]=s2[k]=Data(,,,);
         return;
     }
     int mid=(l+r)/;
     if (pos<=mid) modify(k*,l,mid,pos);
     else modify(k*+,mid+,r,pos);
     s1[k]=s1[k*]+s1[k*+];
     s2[k]=s2[k*+]+s2[k*];
 }
 Data ask1(int k,int l,int r,int x,int y){
     if (l==x&&r==y){
         return s1[k];
     }
     int mid=(l+r)/;
     if (y<=mid) return ask1(k*,l,mid,x,y);
     else
     if (x>mid) return ask1(k*+,mid+,r,x,y);
     else return ask1(k*,l,mid,x,mid)+ask1(k*+,mid+,r,mid+,y);
 }
 Data ask2(int k,int l,int r,int x,int y){
     if (l==x&&r==y){
         return s2[k];
     }
     int mid=(l+r)/;
     if (y<=mid) return ask2(k*,l,mid,x,y);
     else
     if (x>mid) return ask2(k*+,mid+,r,x,y);
     else return ask2(k*+,mid+,r,mid+,y)+ask2(k*,l,mid,x,mid);
 }
 int work(int x,int y){
     Data ans1(,,,),ans2(,,,);
     while (top[x]!=top[y]){
         if (dep[top[x]]<dep[top[y]]){
             ans2=ask1(,,n,dfn[top[y]],dfn[y])+ans2;
             y=fa[top[y]];
         }else{
             ans1=ans1+ask2(,,n,dfn[top[x]],dfn[x]);
             x=fa[top[x]];
         }
     }
     if (x!=y){
         if (dep[x]<dep[y]){
             ans2=ask1(,,n,dfn[son[x]],dfn[y])+ans2;
         }else{
             ans1=ans1+ask2(,,n,dfn[son[y]],dfn[x]);
         }
     }
     return (ans1+ans2).v;
 }
 int main(){
     freopen("tx.in","r",stdin);
     n=read();
     for (int i=;i<n;i++) V[i]=read();
     for (int i=;i<n;i++){
         int x=read()+,y=read()+,v=read();
         add(x,y,v);
     }
     m=read();
     for (int i=;i<=m;i++){
         q[i].x=read()+,q[i].y=read()+,q[i].lim=read();q[i].id=i;
     }
     dfs1(,);dfs2(,);
     std::sort(q+,q++m,cmp);
     std::sort(t+,t++t[],cmp1);
     int h=;build(,,n);
     for (int i=;i<=m;i++){
         while (val[t[h]]<=q[i].lim&&h<=t[]){
             modify(,,n,dfn[go[t[h]]]);
             h++;
         }
         ans[q[i].id]=work(q[i].x,q[i].y);
     }
     for (int i=;i<=m;i++) printf("%d\n",ans[i]);
 }