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| #include<bits/stdc++.h>
#define REG register
using namespace std;
const int Maxn=200005;
inline void read(int& x){
static char c;
while(!isdigit(c=getchar()));x=c^48;
while(isdigit(c=getchar()))x=(x*10)+(c^48);
}
int n,m,k;
struct Edge{int v,nxt;}ed[Maxn<<1];
int head[Maxn],cnt;
inline void adde(int u,int v){ed[++cnt]=(Edge){v,head[u]},head[u]=cnt;}
inline void add(int u,int v){adde(u,v),adde(v,u);}
#define FORE(i,now) for(REG int i=head[now];i;i=ed[i].nxt)
int fat[Maxn],siz[Maxn],dfn[Maxn],tot;
int que[Maxn];
inline bool cmp(int a,int b){return dfn[a]<dfn[b];}
void dfs(int now,int fa){
fat[now]=fa,dfn[now]=++tot,siz[now]=1;
FORE(i,now){
int v=ed[i].v;
if(v==fa) continue;
dfs(v,now);
siz[now]+=siz[v];
}
}
inline void Work(){
read(n),read(m);
for(REG int i=1;i<n;++i){int u,v;read(u),read(v),add(u,v);}
dfs(1,1);
while(m--){
read(k);
for(REG int i=1;i<=k;++i) read(que[i]),que[i]=fat[que[i]];
sort(que+1,que+k+1,cmp);
int flag=1;
for(REG int i=2;i<=k;++i)
if(dfn[que[i]]<dfn[que[i-1]]||dfn[que[i]]>dfn[que[i-1]]+siz[que[i-1]]-1){flag=0;break;}
if(flag) puts("YES");
else puts("NO");
}
getchar(),getchar();
}
int main(){Work();}
|
