[BZO3572][HNOI2014]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('
');
		clear_itree();
	}
	return 0;
}