玄关求条，Only AC test2

#include<bits/stdc++.h>
using namespace std;
const int N=3e5+5;
struct STree{
	struct node{
		int l,r;
		bool dat;
	}t[N<<2];
	inline void push_up(int p){
		t[p].dat=(t[p<<1].dat||t[p<<1|1].dat);
	}
	inline void build(int p,int l,int r){
		t[p].l=l;t[p].r=r;t[p].dat=false;
		if (l==r) return ;
		int mid=(l+r)>>1;
		build(p<<1,l,mid);
		build(p<<1|1,mid+1,r);
	}
	inline void change(int p,int x){
		if (t[p].l==t[p].r){
			t[p].dat=!t[p].dat;
			return ;
		}int mid=(t[p].l+t[p].r)>>1;
		if (x<=mid) change(p<<1,x);
		else change(p<<1|1,x);
		push_up(p);
	}
	inline bool ask(int p,int l,int r){
		if (l<=t[p].l&&t[p].r<=r)
			return t[p].dat;
		int mid=(t[p].l+t[p].r)>>1;
		bool val=false;
		if (l<=mid) val|=ask(p<<1,l,r);
		if (r>mid) val|=ask(p<<1|1,l,r);
		return val;
	}
}st;
int n,q,p[N],tot;
int dep[N],f[N],son[N],sz[N];
int dfn[N],rnk[N],top[N],cnt;
vector<int> edge[N];
inline void dfs1(int x){
	sz[x]=1;
	son[x]=-1;
	for (auto y:edge[x])
		if (!dep[y]){
			dep[y]=dep[x]+1;
			f[y]=x;
			dfs1(y);
			sz[x]+=sz[y];
			if (son[x]==-1||sz[y]>sz[son[x]]) son[x]=y;
		}
}
inline void dfs2(int x,int t){
	top[x]=t;
	dfn[x]=++cnt;
	rnk[cnt]=x;
	if (son[x]==-1) return ;
	dfs2(son[x],t);
	for (auto y:edge[x])
		if (y!=f[x]&&y!=son[x])
			dfs2(y,y);
}
inline bool get_ans(int x,int y){
	bool ans=false;
	while (top[x]!=top[y]){
		if (dep[top[x]]<dep[top[y]]) swap(x,y);
		ans|=st.ask(1,dfn[top[x]],dfn[x]);
		if (ans) return true;
		x=f[top[x]];
	}if (dfn[x]>dfn[y]) swap(x,y);
	return ans|st.ask(1,dfn[x]+1,dfn[y]);
}
int main(){
	cin>>n>>q;
	for (int i=1,x,y;i<n;i++){
		cin>>x>>y;
		edge[x].push_back(y);
		edge[y].push_back(x);
	}dep[1]=1;dfs1(1);dfs2(1,1);
	st.build(1,1,n);
	while (q--){
		char opt;int x,y;
		cin>>opt>>x;
		if (opt!='U') cin>>y;
		if (dep[x]>dep[y]) swap(x,y);
		if (opt=='Q') puts(get_ans(x,y)?"No":"Yes");
		else if (opt=='C') st.change(1,dfn[y]),p[++tot]=dfn[y];
		else st.change(1,p[x]);
	}
	return 0;
}