http://www.lydsy.com/JudgeOnline/problem.php?id=3572
首先我们先构建出虚树
然后在虚树上DP，求出虚树上每个点离最近的临时议事处在哪里
对于虚树上相邻的两个点$u$和$v$，他们连线上一定存在一个分界处，一边一定会去离$u$最近的临时议事处；另一边一定会去离$v$最近的临时议事处
然后就做完了
#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<fstream>
#include<algorithm>
#include<cstring>
#include<string>
#include<cmath>
#include<queue>
#include<stack>
#include<map>
#include<utility>
#include<set>
#include<bitset>
#include<vector>
#include<functional>
#include<deque>
#include<cctype>
#include<climits>
#include<complex>
#include<cassert>
//#include<bits/stdc++.h>适用于CF,UOJ，但不适用于poj
using namespace std;
typedef long long LL;
typedef double DB;
typedef pair<int,int> PII;
typedef pair<DB,DB> PDD;
typedef complex<DB> CP;
typedef vector<int> VI;
#define mmst(a,v) memset(a,v,sizeof(a))
#define mmcy(a,b) memcpy(a,b,sizeof(a))
#define fill(a,l,r,v) fill(a+l,a+r+1,v)
#define re(i,a,b) for(i=(a);i<=(b);i++)
#define red(i,a,b) for(i=(a);i>=(b);i--)
#define fi first
#define se second
#define mp(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define SF scanf
#define PF printf
#define two(k) (1<<(k))
#define SZ(x) (int(x.size()))
#define all(x) (x).begin(),(x).end()
#define ire(i,v,x) for(i=0,v=i<SZ(x)?x[i]:0;i<SZ(x);v=x[++i])
template<class T>inline T sqr(T x){return x*x;}
template<class T>inline void upmin(T &t,T tmp){if(t>tmp)t=tmp;}
template<class T>inline void upmax(T &t,T tmp){if(t<tmp)t=tmp;}
inline int sgn(DB x){if(abs(x)<1e-9)return 0;return(x>0)?1:-1;}
const DB Pi=acos(-1.0);
int gint()
{
int res=0;bool neg=0;char z;
for(z=getchar();z!=EOF && z!=‘-‘ && !isdigit(z);z=getchar());
if(z==EOF)return 0;
if(z==‘-‘){neg=1;z=getchar();}
for(;z!=EOF && isdigit(z);res=res*10+z-‘0‘,z=getchar());
return (neg)?-res:res;
}
LL gll()
{
LL res=0;bool neg=0;char z;
for(z=getchar();z!=EOF && z!=‘-‘ && !isdigit(z);z=getchar());
if(z==EOF)return 0;
if(z==‘-‘){neg=1;z=getchar();}
for(;z!=EOF && isdigit(z);res=res*10+z-‘0‘,z=getchar());
return (neg)?-res:res;
}
const int maxn=300100;
int n;
VI e[maxn];
const int up=25;
int dep[maxn],jump[maxn][up+1];
int head,tail,que[maxn];
int sz[maxn],idx[maxn];
void bfs()
{
int i,j;
dep[que[head=tail=1]=1]=1;
re(j,0,up)jump[1][j]=1;
while(head<=tail)
{
int u=que[head++];
re(i,0,SZ(e[u])-1)if(!dep[e[u][i]])
{
int v=e[u][i];
dep[que[++tail]=v]=dep[u]+1;
jump[v][0]=u;
re(j,1,up)jump[v][j]=jump[jump[v][j-1]][j-1];
}
}
red(i,tail,1)
{
int u=que[i];
sz[u]=1;
re(j,0,SZ(e[u])-1)if(dep[e[u][j]]>dep[u])sz[u]+=sz[e[u][j]];
}
idx[1]=1;
re(i,1,tail)
{
int u=que[i],tmp=0;
re(j,0,SZ(e[u])-1)if(dep[e[u][j]]>dep[u]){int v=e[u][j];idx[v]=idx[u]+tmp+1,tmp+=sz[v];}
}
}
int swim(int x,int H){for(int i=0;H;H>>=1,i++)if(H&1)x=jump[x][i];return x;}
int ask_lca(int x,int y)
{
if(dep[x]<dep[y])swap(x,y);
x=swim(x,dep[x]-dep[y]);
if(x==y)return x;
int i;red(i,up,0)if(jump[x][i]!=jump[y][i])x=jump[x][i],y=jump[y][i];
return jump[x][0];
}
int m,h[maxn],h2[maxn];
int mark[maxn],ans[maxn];
VI to[maxn];
int ge,w[maxn];
bool cmp(int a,int b){return idx[a]<idx[b];}
int top,sta[maxn];
void addedge(int u,int v){to[u].pb(v);to[v].pb(u);}
void build()
{
int i;
re(i,1,ge)to[w[i]].clear();
sort(h+1,h+m+1,cmp);
ge=0;
sta[top=1]=1;
re(i,2,m)
{
while(1)
{
int lca=ask_lca(h[i],sta[top]);
if(lca==sta[top])break;
if(idx[lca]>idx[sta[top-1]])
{
w[++ge]=sta[top];
addedge(sta[top],lca);
sta[top]=lca;
}
else
{
addedge(sta[top],sta[top-1]);
w[++ge]=sta[top--];
}
}
sta[++top]=h[i];
}
while(top>=2)addedge(sta[top],sta[top-1]),w[++ge]=sta[top--];
w[++ge]=sta[top--];
}
const int inf=0x3f3f3f3f;
PII f[maxn];
int fa[maxn];
void solve()
{
int i,j;
re(i,1,ge)fa[w[i]]=0,f[w[i]]=mark[w[i]]?mp(0,w[i]):mp(inf,0);
que[head=tail=1]=1;
while(head<=tail)
{
int u=que[head++];
re(j,0,SZ(to[u])-1)if(to[u][j]!=fa[u])fa[que[++tail]=to[u][j]]=u;
}
red(i,tail,2)
{
int u=que[i],v=fa[u];
upmin(f[v],mp(f[u].fi+dep[u]-dep[v],f[u].se));
}
re(i,2,tail)
{
int u=que[i],v=fa[u];
upmin(f[u],mp(f[v].fi+dep[u]-dep[v],f[v].se));
}
re(i,1,tail)
{
int x=que[i],tmp=sz[x];
re(j,0,SZ(to[x])-1)if(to[x][j]!=fa[x])
{
int y=to[x][j],z=swim(y,dep[y]-dep[x]-1);
tmp-=sz[z];
}
ans[f[x].se]+=tmp;
}
re(i,2,tail)
{
int x=que[i],y=fa[x],dist=dep[x]-dep[y],z=swim(x,dist-1);
if(f[x].se==f[y].se)
ans[f[x].se]+=sz[z]-sz[x];
else
{
int d=(f[y].fi-f[x].fi+dist)/2.0;
if((f[y].fi-f[x].fi+dist)%2==0 && f[y].se<f[x].se)d--;
int u=swim(x,d);
ans[f[y].se]+=sz[z]-sz[u];
ans[f[x].se]+=sz[u]-sz[x];
}
}
}
int main()
{
freopen("worldtree.in","r",stdin);
freopen("worldtree.out","w",stdout);
int i;
n=gint();
re(i,1,n-1){int x=gint(),y=gint();e[x].pb(y);e[y].pb(x);}
bfs();
int Q=gint();
while(Q--)
{
m=gint();
re(i,1,m)mark[h2[i]=h[i]=gint()]=i;
if(!mark[1])h[++m]=1;
build();
solve();
re(i,1,m)if(mark[h2[i]])PF("%d ",ans[h2[i]]),ans[h2[i]]=mark[h2[i]]=0;PF("\n");
}
return 0;
}
时间： 2024-12-08 13:22:00