我有个同学昨天晚上不知道为什么一点才睡觉，还要大半夜把我叫起来。今天迷迷糊糊敲了个代码让我找bug，然而我也没睡好，求助万能的谷民。树剖求调。

题目：P2590 [ZJOI2008]树的统计

传送门：https://www.luogu.com.cn/problem/P2590

代码

#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read() {
	int x=0,f=0;char ch=getchar();
	for(;!isdigit(ch);ch=getchar()) f|=(ch=='-');
    for(;isdigit(ch);ch=getchar()) x=(x<<1)+(x<<3)+(ch^48);
	return f?-x:x;
}
void print(int x) {
	if(x<0) putchar('-'),x=-x;
	if(x>9) print(x/10);
	putchar(x%10+48);
}   
struct node{
	int next,to;
}e[1023213];    
int head[10231312],cnt,tot,n,m,x,y,z,a[10231312];
int pre[10231231],dfn[10231312],top[10231312],dep[1023123],fa[10213123],size[1023123],son[1023123];
void add(int u,int v) {
	e[++cnt].next=head[u];
	e[cnt].to=v;
	head[u]=cnt;
}
namespace ss{      
	 #define lson pos<<1
	 #define rson pos<<1|1
	 struct node{      
	    int sum,maxx,lazy;              
 	 }tree[1023123];     
	 void build(int pos,int l,int r) {
	 	if (l==r) {
	 		tree[pos].sum=a[pre[l]]; 
			tree[pos].maxx=tree[pos].sum; 
			return ;          
		}                        
		int mid=l+r>>1;           
  		build(lson,l,mid); build(rson,mid+1,r);            
		tree[pos].sum=tree[lson].sum+tree[rson].sum;       
		tree[pos].maxx=max(tree[lson].maxx,tree[rson].maxx);
	 }     
	 void change(int pos,int l,int r,int L,int R,int k) {
	 	if (l>=L && r<=R) {
	 		 tree[pos].sum=k; tree[pos].maxx=k;
			 return ;
		 }
		 int mid=l+r>>1; 
		 if (L<=mid) change(lson,l,mid,L,R,k);
	     if (R>mid) change(rson,mid+1,r,L,R,k);
		 tree[pos].sum=tree[lson].sum+tree[rson].sum;
	     tree[pos].maxx=(tree[lson].maxx,tree[rson].maxx);
	 } 
	 int query(int pos,int l,int r,int L,int R) {
	 	if (l>=L && r<=R) return tree[pos].sum;
		int mid=l+r>>1,res=0; 
		if (L<=mid) res+=query(lson,l,mid,L,R);
		if (R>mid) res+=query(rson,mid+1,r,L,R);
	    return res;
	 }
	 int m_query(int pos,int l,int r,int L,int R) {
	 	if (l>=L && r<=R) return tree[pos].maxx;
	 	int mid=l+r>>1,res=-0x7ffffff; 
	 	if (L<=mid) res=max(res,m_query(lson,l,mid,L,R));
	 	if (R>mid) res=max(res,m_query(rson,mid+1,r,L,R));
	 	return res;
 	 }
}                
namespace sp{
	void dfs1(int now,int Fa){
	    size[now]=1; dep[now]=dep[Fa]+1; fa[now]=Fa;
	    for (int i=head[now];i;i=e[i].next) {
	    	if (e[i].to==Fa) continue;
	    	dfs1(e[i].to,now);
	    	size[now]+=size[e[i].to];
	        if (size[son[now]]<size[e[i].to]) son[now]=e[i].to;
		}
	}
    void dfs2(int now,int Top) {
    	dfn[now]=++tot; pre[tot]=now; top[now]=Top;
    	if (son[now]) dfs2(son[now],Top);
 	    for (int i=head[now];i;i=e[i].next) {
 	    	if (e[i].to==fa[now]||e[i].to==son[now]) continue;
 	    	dfs2(e[i].to,e[i].to);
		}    
	}       
	int query(int x,int y) {
	    int res=0;
	    while(top[x]!=top[y]) {
	    	if (dep[top[x]]<dep[top[y]]) swap(x,y);
	    	res+=ss::query(1,1,n,dfn[top[x]],dfn[x]);
	    	x=fa[top[x]];
		}
		if (dep[x]>dep[y]) swap(x,y);
	    res+=ss::query(1,1,n,dfn[x],dfn[y]);
	    return res;      
	}       
	int m_query(int x,int y) {
		int res=-0x7ffffff;           
		while(top[x]!=top[y]) {     
			if (dep[top[x]]<dep[top[y]]) swap(x,y);
			res=max(res,ss::m_query(1,1,n,dfn[top[x]],dfn[x]));
			x=fa[top[x]];       
		}                    
		if (dep[x]>dep[y]) swap(x,y);
		res=max(res,ss::m_query(1,1,n,dfn[x],dfn[y]));
		return res;
	}       
}        
signed main() {     
    n=read();	   
    for (int i=1;i<n;++i) {     
    	x=read(); y=read();   
    	add(x,y); add(y,x); 
	}       
    for (int i=1;i<=n;++i) a[i]=read(); 
    sp::dfs1(1,0); sp::dfs2(1,1); 
	ss::build(1,1,n); 
    m=read();
	for (int i=1;i<=m;++i) {
		string s;
		cin>>s;
		if (s[1]=='M') {
			x=read(); y=read();
			print(sp::m_query(x,y)); putchar('\n');
		}    
		else if (s[1]=='S') {
		    x=read(); y=read();
		    print(sp::query(x,y)); putchar('\n');
		}   
		else if (s[1]=='H') {
		    x=read(); z=read();
		    ss::change(1,1,n,dfn[x],dfn[x],z);
		}
	}            
    return 0;
}