解题：LNOI 2014 LCA

题面

这题有点意思

转化问题，我们把询问区间的点到根链加，再查询询问点到根的权值和就是每个询问的答案。

然后如果你数据结构没学傻只需要差分一下就可以扫一遍出解了

 #include<cstdio>
 #include<vector>
 #include<cstring>
 #include<algorithm>
 #define vpii vector<pair<int,int> >
 #define vpit vector<pair<int,int> >::iterator
 using namespace std;
 const int N=,M=,mod=;
 int p[N],noww[M],goal[M],val[M],laz[M],siz[N];
 int far[N],dep[N],imp[N],dfn[N],top[N],ans[N];
 int n,q,t1,t2,t3,cnt,tot; vpii lp[N],rp[N];
 void Add(int &x,int y)
 {
     x+=y;
     if(x>=mod) x-=mod;
 }
 void Link(int f,int t)
 {//printf("Link %d with %d",f,t);
     noww[++cnt]=p[f];
     goal[cnt]=t,p[f]=cnt;
     noww[++cnt]=p[t];
     goal[cnt]=f,p[t]=cnt;
 }
 void Release(int nde,int l,int r)
 {
     if(laz[nde])
     {
         int mid=(l+r)/,ls=*nde,rs=*nde+,&lz=laz[nde];
         val[ls]+=lz*(mid-l+),laz[ls]+=lz;
         val[rs]+=lz*(r-mid),laz[rs]+=lz,lz=;
     }
 }
 void Change(int nde,int l,int r,int ll,int rr,int tsk)
 {
     if(l>rr||r<ll)
         return ;
     else if(l>=ll&&r<=rr)
         val[nde]+=tsk*(r-l+),laz[nde]+=tsk;
     else
     {
         int mid=(l+r)/,ls=*nde,rs=*nde+; Release(nde,l,r);
         Change(ls,l,mid,ll,rr,tsk),Change(rs,mid+,r,ll,rr,tsk);
         val[nde]=val[ls]+val[rs];
     }
 }
 int Query(int nde,int l,int r,int ll,int rr)
 {
     if(l>rr||r<ll)
         return ;
     else if(l>=ll&&r<=rr)
         return val[nde];
     else
     {
         int mid=(l+r)/,ls=*nde,rs=*nde+; Release(nde,l,r);
         return Query(ls,l,mid,ll,rr)+Query(rs,mid+,r,ll,rr);
     }
 }
 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)
         {
             DFS(goal[i],nde,dth+);
             siz[nde]+=siz[goal[i]];
             if(siz[goal[i]]>tmp)
                 tmp=siz[goal[i]],imp[nde]=goal[i];
         }
 }
 void Decompose(int nde,int tpp)
 {
     dfn[nde]=++tot,top[nde]=tpp;
     if(imp[nde])
     {
         Decompose(imp[nde],tpp);
         for(int i=p[nde];i;i=noww[i])
             if(goal[i]!=imp[nde]&&goal[i]!=far[nde])
                 Decompose(goal[i],goal[i]);
     }
 }
 void Chain_Change(int x,int y,int v)
 {
     while(top[x]!=top[y])
     {
         if(dep[top[x]]<dep[top[y]]) swap(x,y);
         Change(,,n,dfn[top[x]],dfn[x],v),x=far[top[x]];
     }
     if(dep[x]>dep[y]) swap(x,y);
     Change(,,n,dfn[x],dfn[y],v);
 }
 int Chain_Query(int x,int y)
 {
     int ret=;
     while(top[x]!=top[y])
     {
         if(dep[top[x]]<dep[top[y]]) swap(x,y);
         ret+=Query(,,n,dfn[top[x]],dfn[x]),x=far[top[x]];
     }
     if(dep[x]>dep[y]) swap(x,y);
     ret+=Query(,,n,dfn[x],dfn[y]); return ret;
 }
 int main()
 {
     scanf("%d%d",&n,&q);
     for(int i=;i<=n;i++)
         scanf("%d",&t1),Link(t1+,i);
     for(int i=;i<=q;i++)
     {
         scanf("%d%d%d",&t1,&t2,&t3);
         lp[t1].push_back(make_pair(i,t3+));
         rp[t2+].push_back(make_pair(i,t3+));
     }
     DFS(,,),Decompose(,);
     for(int i=;i<=n;i++)
     {
         Chain_Change(,i,);
         for(vpit it=lp[i].begin();it!=lp[i].end();it++)
             ans[it->first]-=Chain_Query(,it->second);//,printf("%d-=%d\n",it->first,Chain_Query(1,it->second));
         for(vpit it=rp[i].begin();it!=rp[i].end();it++)
             ans[it->first]+=Chain_Query(,it->second);//,printf("%d+=%d\n",it->first,Chain_Query(1,it->second));
     }
     for(int i=;i<=q;i++)
         printf("%d\n",ans[i]%mod);
     return ;
 }