[BZO3572]世界树：虚树+倍增

分析

思维难度几乎为\(0\)的虚树码农（并不）题。

代码

#include <bits/stdc++.h>
#define rin(i,a,b) for(register int i=(a);i<=(b);++i)
#define irin(i,a,b) for(register int i=(a);i>=(b);--i)
#define trav(i,a) for(register int i=head[a];i;i=e[i].nxt)
#define itrav(i,a) for(register int i=ihead[a];i;i=ie[i].nxt)
typedef long long LL;
using std::cin;
using std::cout;
using std::endl;

inline int read(){
    int x=0,f=1;char ch=getchar();
    while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
    while(isdigit(ch)){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

const int MAXN=3e5+5;
int n,q,ecnt,head[MAXN];
int tot,id[MAXN],num[MAXN],len,st[MAXN<<1][21],pos[MAXN];
int dep[MAXN],siz[MAXN],anc[MAXN][21];
int m,mm,h[MAXN<<1],hh[MAXN],top,sta[MAXN];
int iecnt,ihead[MAXN];
int ans[MAXN];
bool isc[MAXN];

struct Edge{
    int to,nxt;
}e[MAXN<<1];

inline void add_edge(int bg,int ed){
    ++ecnt;
    e[ecnt].to=ed;
    e[ecnt].nxt=head[bg];
    head[bg]=ecnt;
}

void dfs1(int x,int pre,int depth){
    id[x]=++tot;
    num[tot]=x;
    st[++len][0]=id[x];
    pos[x]=len;
    dep[x]=depth;
    siz[x]=1;
    anc[x][0]=pre;
    trav(i,x){
        int ver=e[i].to;
        if(ver==pre) continue;
        dfs1(ver,x,depth+1);
        st[++len][0]=id[x];
        siz[x]+=siz[ver];
    }
}

void buildst(){
    int lim=log2(len);
    rin(i,1,lim) rin(j,1,len-(1<<i)+1)
        st[j][i]=std::min(st[j][i-1],st[j+(1<<(i-1))][i-1]);
}

void buildanc(){
    rin(i,1,20) rin(j,1,n)
        anc[j][i]=anc[anc[j][i-1]][i-1];
}

inline int lca(int x,int y){
    x=pos[x],y=pos[y];
    if(x>y) std::swap(x,y);
    int lim=log2(y-x+1);
    return num[std::min(st[x][lim],st[y-(1<<lim)+1][lim])];
}

inline bool cmp(int x,int y){
    return id[x]<id[y];
}

struct iedge{
    int to,nxt;
}ie[MAXN];

inline void add_iedge(int bg,int ed){
    ++iecnt;
    ie[iecnt].to=ed;
    ie[iecnt].nxt=ihead[bg];
    ihead[bg]=iecnt;
}

void build_itree(){
    std::sort(h+1,h+m+1,cmp);
    rin(i,2,mm) h[++m]=lca(h[i-1],h[i]);
    h[++m]=1;
    std::sort(h+1,h+m+1,cmp);
    m=std::unique(h+1,h+m+1)-h-1;
    top=0;
    rin(i,1,m){
        while(top&&id[h[i]]>id[sta[top]]+siz[sta[top]]-1) add_iedge(sta[top-1],sta[top]),--top;
        sta[++top]=h[i];
    }
    while(top>1) add_iedge(sta[top-1],sta[top]),--top;
    --top;
}

struct ctrl{
    int pos,dis;
    inline friend bool operator < (ctrl A,ctrl B){
        return A.dis==B.dis?A.pos<B.pos:A.dis<B.dis;
    }
}c[MAXN];

void dfs2(int x){
    if(isc[x]) c[x]=(ctrl){x,0};
    else c[x]=(ctrl){0,(int)1e9};
    itrav(i,x){
        int ver=ie[i].to;
        dfs2(ver);
        c[x]=std::min(c[x],(ctrl){c[ver].pos,c[ver].dis+dep[ver]-dep[x]});
    }
}

void dfs3(int x,int pre){
    if(pre) c[x]=std::min(c[x],(ctrl){c[pre].pos,c[pre].dis+dep[x]-dep[pre]});
    itrav(i,x){
        int ver=ie[i].to;
        dfs3(ver,x);
    }
}

inline int getveranc(int x,int pre){
    int ret=x;
    irin(i,20,0)
        if(dep[anc[ret][i]]>dep[pre])
            ret=anc[ret][i];
    return ret;
}

inline int climb(int x,int y){
    int ret=x,tt=0;
    while(y){
        if(y&1) ret=anc[ret][tt];
        ++tt;
        y>>=1;
    }
    return ret;
}

void dfs4(int x,int pre){
    ans[c[x].pos]+=siz[x];
    itrav(i,x){
        int ver=ie[i].to,veranc=getveranc(ver,x);
        dfs4(ver,x);
        ans[c[x].pos]-=siz[veranc];
        if(c[x].pos==c[ver].pos)
            ans[c[x].pos]+=siz[veranc]-siz[ver];
        else{
            int mid=0;
            if((dep[ver]-dep[x]+c[ver].dis-c[x].dis)&1) mid=dep[ver]-(((dep[x]+dep[ver]+c[ver].dis-c[x].dis)>>1)+1);
            else if(c[x].pos<c[ver].pos) mid=dep[ver]-(((dep[x]+dep[ver]+c[ver].dis-c[x].dis)>>1)+1);
            else mid=dep[ver]-((dep[x]+dep[ver]+c[ver].dis-c[x].dis)>>1);
            mid=climb(ver,mid);
            ans[c[x].pos]+=siz[veranc]-siz[mid];
            ans[c[ver].pos]+=siz[mid]-siz[ver];
        }
    }
}

/*
const int MAXN=3e5+5;
int n,q,ecnt,head[MAXN];
int tot,id[MAXN],num[MAXN],len,st[MAXN<<1][21],pos[MAXN];
int dep[MAXN],siz[MAXN],anc[MAXN][21];
int m,mm,h[MAXN<<1],hh[MAXN],top,sta[MAXN];
int iecnt,ihead[MAXN];
int ans[MAXN];
bool isc[MAXN];
*/

void clear_itree(){
    iecnt=0;
    rin(i,1,m) ihead[h[i]]=ans[h[i]]=0,isc[h[i]]=false;
}

int main(){
    n=read();
    rin(i,2,n){
        int u=read(),v=read();
        add_edge(u,v);
        add_edge(v,u);
    }
    dfs1(1,0,1);
    buildst();
    buildanc();
    q=read();
    while(q--){
        m=mm=read();
        rin(i,1,m) h[i]=hh[i]=read(),isc[h[i]]=true;
        build_itree();
        dfs2(1);
        dfs3(1,0);
        dfs4(1,0);
        rin(i,1,mm) printf("%d ",ans[hh[i]]);
        putchar('\n');
        clear_itree();
    }
    return 0;
}