CHANGE 直接 RE，QMAX WA 了，交上去 MLE。

#include<bits/stdc++.h>
using namespace std;
const int N=3e4+4;
#define ll long long
#define ls(x) x<<1
#define rs(x) x<<1|1
#define inf 1e18
int n,q;
int u,v,x,y;
int a[N],cnt;
int sz[N],son[N],dfn[N],top[N],fa[N],rnk[N],dep[N],siz[N<<2];
ll w[N<<2],maxx[N<<2];
vector<int>G[N];
string s;
void dfs1(int u,int father){
	dep[u]=dep[father]+1;
	fa[u]=father;
	sz[u]=1;
	for(int i=0;i<G[u].size();i++){
		int v=G[u][i];
		if(v==father){
			continue;
		}
		dfs1(v,u);
		sz[u]+=sz[v];
		if(sz[v]>sz[son[u]]){
			son[u]=v;
		}
	}
}
void dfs2(int u,int tp){
	top[u]=tp,dfn[u]=++cnt;
	rnk[dfn[u]]=u;
	if(!son[u]){
		return;
	}
	dfs2(son[u],tp);
	for(int i=0;i<G[u].size();i++){
		int v=G[u][i];
		if(v!=fa[u]&&v!=son[u]){
			dfs2(v,v);
		}
	} 
}
void pushup(int u){
	w[u]=w[ls(u)]+w[rs(u)];
	maxx[u]=max(maxx[ls(u)],maxx[rs(u)]);
}
void build(int u,int l,int r){
	if(l==r){
		siz[u]=1;
		w[u]=a[rnk[l]];
		return;
	}
	siz[u]=r-l+1;
	int mid=l+r>>1;
	build(ls(u),l,mid);
	build(rs(u),mid+1,r);
	pushup(u);
}
void update(int u,int l,int r,int pos,int p){
	if(l==pos&&r==pos){
		w[u]=maxx[u]=p; return;
	}
	int mid=l+r>>1;
	update(ls(u),l,mid,pos,p);
	update(rs(u),mid+1,r,pos,p);
	pushup(u);
}
ll qry_max(int u,int l,int r,int L,int R){
	if(L<=l&&r<=R){
		return maxx[u];
	}
	else if(!(r<L||R<l)){
		int mid=l+r>>1;
		return max(qry_max(ls(u),l,mid,L,R),qry_max(rs(u),mid+1,r,L,R));
	}
return -inf;
}
ll qry_sum(int u,int l,int r,int L,int R){
	if(L<=l&&r<=R){
		return w[u];
	}
	else if(!(r<L||R<l)){
		int mid=l+r>>1;
		return qry_sum(ls(u),l,mid,L,R)+qry_sum(rs(u),mid+1,r,L,R);
	}
return 0;
}
ll ask(int x,int y,bool type){
	ll ans=0;
	while(top[x]!=top[y]){
		if(dep[top[x]]<dep[top[y]]){
			swap(x,y);
		}
		if(type==0){
			ans=max(ans,qry_max(1,1,n,dfn[top[x]],dfn[x]));
		}
		else{
			ans+=qry_sum(1,1,n,dfn[top[x]],dfn[x]);
		}
		x=fa[top[x]];
	}
	if(dfn[x]>dfn[y]){
		swap(x,y);
	}
	if(type==0){
		return max(ans,qry_max(1,1,n,dfn[x],dfn[y]));
	}
return ans+qry_sum(1,1,n,dfn[x],dfn[y]);
}
int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin>>n;
	for(int i=1;i<n;i++){
		cin>>u>>v;
		G[u].push_back(v);
		G[v].push_back(u);
	} 
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	dfs1(1,0);
	dfs2(1,0);
	build(1,1,n);
	cin>>q;
	while(q--){
		cin>>s>>x>>y;
		if(s=="CHANGE"){
			update(1,1,n,x,y);
		} 
		else if(s=="QMAX"){
			cout<<ask(x,y,0)<<"\n";
		} 
		else{
			cout<<ask(x,y,1)<<"\n";
		}
	}
return 0;
}