BZOJ 3091: 城市旅行 lct 期望 splay

https://www.lydsy.com/JudgeOnline/problem.php?id=3091

https://blog.csdn.net/popoqqq/article/details/40823659

看题解吧，没什么好解释的。。。。板子题，

我觉得以后我写lct都可以像这样专门写个rev和add的函数出来，很好用。

 #include<iostream>
 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<cmath>
 #include<queue>
 using namespace std;
 const int maxn=;
 int n,m;
 int fa[maxn]={},ch[maxn][]={};
 long long siz[maxn]={},val[maxn]={},sum[maxn]={};
 long long lsum[maxn]={},rsum[maxn]={};
 long long num[maxn]={};long long ad[maxn]={};
 int rev[maxn]={};int sta[maxn]={},tail=;
 inline void updata(int x){
     sum[x]=sum[ch[x][]]+sum[ch[x][]]+val[x];
     siz[x]=siz[ch[x][]]+siz[ch[x][]]+;

     lsum[x]=lsum[ch[x][]]+lsum[ch[x][]]+(sum[ch[x][]]+val[x])*(siz[ch[x][]]+);
     rsum[x]=rsum[ch[x][]]+rsum[ch[x][]]+(sum[ch[x][]]+val[x])*(siz[ch[x][]]+);

     num[x]=num[ch[x][]]+num[ch[x][]]
     +lsum[ch[x][]]*(siz[ch[x][]]+)
     +rsum[ch[x][]]*(siz[ch[x][]]+)
     +val[x]*(siz[ch[x][]]+)*(siz[ch[x][]]+);
 }
 inline long long hex(long long x){return x*(x+)/;}
 inline long long hex2(long long x){return x*(x+)*(x+)/;}
 void Add(int x,long long v){
     ad[x]+=v; sum[x]+=siz[x]*v; val[x]+=v;
     lsum[x]+=hex(siz[x])*v;
     rsum[x]+=hex(siz[x])*v;
     num[x]+=hex2(siz[x])*v;
 }
 void Rev(int x){
     swap(ch[x][],ch[x][]);
     swap(lsum[x],rsum[x]);
     rev[x]^=;
 }
 inline void downdata(int x){
     if(rev[x]){
         if(ch[x][])Rev(ch[x][]);
         if(ch[x][])Rev(ch[x][]);
         updata(x);
         rev[x]=;
     }
     if(ad[x]){
         if(ch[x][])Add(ch[x][],ad[x]);
         if(ch[x][])Add(ch[x][],ad[x]);
         updata(x);
         ad[x]=;
     }
 }
 inline bool isroot(int x){return ch[fa[x]][]!=x&&ch[fa[x]][]!=x;}
 void rotate(int x){
     int y=fa[x];int fy=fa[y];
     int l=ch[y][]==x?:;int r=l^;
     if(!isroot(y)){
         if(ch[fy][]==y)ch[fy][]=x;
         else ch[fy][]=x;
     }
     fa[ch[x][r]]=y;fa[y]=x;fa[x]=fy;
     ch[y][l]=ch[x][r];ch[x][r]=y;
     updata(y);
 }
 void Splay(int x){
     int y,fy,w=x;sta[++tail]=x;
     while(!isroot(w)){ sta[++tail]=fa[w]; w=fa[w]; }
     while(tail)downdata(sta[tail--]);
     while(!isroot(x)){
         y=fa[x];fy=fa[y];
         if(!isroot(y)){
             if((ch[fy][]==y)^(ch[y][]==x)) rotate(x);
             else rotate(y);
         }
         rotate(x);
     }updata(x);
 }
 void Access(int x){
     int y=;
     while(x){
         Splay(x);ch[x][]=y;
         updata(x);
         y=x;x=fa[y];
     }
 }
 int findfa(int x){
     Access(x);Splay(x);
     while(ch[x][])x=ch[x][];
     return x;
 }
 void Reverse(int x){
     Access(x);Splay(x);
     Rev(x);
 }
 void Cut(int x,int y){
     Reverse(x);Access(y);Splay(y);
     if(ch[y][]==x&&!ch[x][]){fa[x]=;ch[y][]=;updata(y);}
 }
 void Link(int x,int y){
     Reverse(x);
     fa[x]=y;
 }
 long long mgcd(long long x,long long y){
     long long z;
     while(y){
         z=x%y;x=y;y=z;
     }return x;
 }
 int main(){
     //freopen("a.in","r",stdin);
     //freopen("a.out","w",stdout);
     scanf("%d%d",&n,&m);
     for(int i=;i<=n;i++){scanf("%lld",&val[i]);siz[i]=;sum[i]=lsum[i]=rsum[i]=num[i]=val[i];}
     int x,y,op;long long v,aa,bb;
     for(int i=;i<n;i++){
         scanf("%d%d",&x,&y); if(findfa(x)!=findfa(y))Link(x,y);
     }
     for(int i=;i<=m;i++){
         scanf("%d%d%d",&op,&x,&y);
         if(op==){
             if(findfa(x)==findfa(y))Cut(x,y);
         }
         else if(op==){
             if(findfa(x)!=findfa(y))Link(x,y);
         }
         else if(op==){
             scanf("%lld",&v);
             if(findfa(x)==findfa(y)){
                 Reverse(x);Access(y);Splay(y);
                 Add(y,v);
             }
         }
         else{
             if(findfa(x)!=findfa(y)){printf("-1\n");}
             else{
                 Reverse(x);Access(y);Splay(y);
                 aa=num[y];bb=hex(siz[y]);
                 v=mgcd(aa,bb);
                 printf("%lld/%lld\n",aa/v,bb/v);
             }
         }
     }
 }