[BZOJ4539][HNOI2016]树(主席树)

#include<cstdio>
#include<algorithm>
#include<iostream>
#define rep(i,l,r) for (int i=l; i<=r; i++)
typedef long long ll;
using namespace std;

const int N=100100,M=2000100;
int n,m,tot,dfn,sm[M],ls[M],rs[M],rt[N],lf[N],rg[N],id[N];
struct P{ int id,rt,fa; ll l,r; }a[N];

template<typename T>inline void rd(T &x){
   int t; char ch;
   for (t=0; !isdigit(ch=getchar()); t=(ch==‘-‘));
   for (x=ch-‘0‘; isdigit(ch=getchar()); x=x*10+ch-‘0‘);
   if (t) x=-x;
}

void ins(int x,int &y,int L,int R,int k){
   y=++tot; sm[y]=sm[x]+1;
   if (L==R) return; int mid=(L+R)>>1;
   if (k<=mid) rs[y]=rs[x],ins(ls[x],ls[y],L,mid,k);
      else ls[y]=ls[x],ins(rs[x],rs[y],mid+1,R,k);
}

int que(int k,int z){
   int L=1,R=n,mid,t,x=rt[lf[k]-1],y=rt[rg[k]];
   while (L<R){
      mid=(L+R)>>1; t=sm[ls[y]]-sm[ls[x]];
      if (z<=t) R=mid,x=ls[x],y=ls[y];
         else L=mid+1,z-=t,x=rs[x],y=rs[y];
   }
   return L;
}

int getid(ll x,int ed){
   int L=1,R=ed+1,mid;
   while (L+1<R){
      mid=(L+R)>>1;
      if (a[mid].l<=x) L=mid; else R=mid;
   }
   return L;
}

struct T{
   int tot,fst[N],pnt[N<<1],len[N<<1],nxt[N<<1];
   int fa[N],sz[N],son[N],anc[N];
   ll d[N];
   void add(int x,int y,int z)
   { pnt[++tot]=y; len[tot]=z; nxt[tot]=fst[x]; fst[x]=tot; }
   
   void dfs(int x){
      int p; sz[x]=1;
      for (p=fst[x]; p; p=nxt[p]){
         int y=pnt[p];
         if (y!=fa[x]){
            fa[y]=x; d[y]=d[x]+len[p];
            dfs(y); sz[x]+=sz[y];
            if (sz[y]>sz[son[x]]) son[x]=y;
         }
      }
   }
   
   void nbr(int x,int tp){
      lf[x]=rg[x]=++dfn; id[dfn]=x; anc[x]=tp; int p;
      if (son[x]) nbr(son[x],tp),rg[x]=rg[son[x]];
      for (p=fst[x]; p; p=nxt[p]){
         int y=pnt[p];
         if (y!=fa[x] && y!=son[x]) nbr(y,y),rg[x]=rg[y];
      }
   }
   
   void div(int x,int tp){
      anc[x]=tp; int p;
      if (son[x]) div(son[x],tp);
      for (p=fst[x]; p; p=nxt[p]){
         int y=pnt[p];
         if (y!=fa[x] && y!=son[x]) div(y,y);
      }
   }
   
   int lca(int x,int y){
      for (; anc[x]!=anc[y]; x=fa[anc[x]])
         if (d[anc[x]]<d[anc[y]]) swap(x,y);
      return (d[x]<d[y]) ? x : y;
   }
   
   int gettp(int x,int y){
      int z;
      for (; anc[x]!=anc[y]; x=fa[anc[x]]) z=anc[x];
      return (x==y) ? z : son[y];
   }
   
   void build(){
      rep(i,1,n) ins(1,n,rt[i-1],rt[i],id[i]);
   }
   
   ll dist(int x,int y){ return d[x]+d[y]-(d[lca(x,y)]<<1); }
}t1,t2;

int main(){
   freopen("bzoj4539.in","r",stdin);
   freopen("bzoj4539.out","w",stdout);
   rd(n); rd(m); int cas,z; ll x,y;
   rd(cas);
   rep(i,1,n-1) rd(x),rd(y),t1.add(x,y,1),t1.add(y,x,1);
   t1.dfs(1); t1.nbr(1,1);
   rep(i,1,n) ins(rt[i-1],rt[i],1,n,id[i]);
   a[1].id=1; a[1].rt=1; a[1].l=1; a[1].r=n;
   rep(i,1,m){
      rd(x); rd(y);
      a[i+1].rt=x; a[i+1].id=i+1;
      a[i+1].l=a[i].r+1; a[i+1].r=a[i].r+t1.sz[x];
      z=getid(y,i); a[i+1].fa=y=que(a[z].rt,y-a[z].l+1);
      t2.add(z,i+1,t1.d[y]-t1.d[a[z].rt]+1);
   }
   t2.dfs(1); t2.div(1,1); int u,v,w; ll ans;
   while (cas--){
      rd(x); rd(y); u=getid(x,m+1); v=getid(y,m+1); w=t2.lca(u,v);
      x=que(a[u].rt,x-a[u].l+1); y=que(a[v].rt,y-a[v].l+1);
      if (u==v) printf("%lld\n",t1.dist(x,y));
      else{
         if (u==w) swap(u,v),swap(x,y);
         if (v==w){
            v=t2.gettp(u,w);
            ans=t1.d[x]-t1.d[a[u].rt]+t2.d[u]-t2.d[v];
            x=a[v].fa; ans+=t1.dist(x,y)+1;
         }else{
            ans=t1.d[x]-t1.d[a[u].rt]+t1.d[y]-t1.d[a[v].rt]+t2.dist(u,v);
            u=t2.gettp(u,w); v=t2.gettp(v,w);
            x=a[u].fa; y=a[v].fa;
            ans-=(t1.d[t1.lca(x,y)]-t1.d[a[w].rt])<<1;
         }
         printf("%lld\n",ans);
      }
   }
   return 0;
}