树链剖分+树状数组，不知道错在哪里，希望大佬出手相助，万分感谢！

#include<bits/stdc++.h>
using namespace std;
int n,m;
#define rank egweg
int const N=2e5+10;
struct edge{
	int u,v,w;
}e[N];
int cnt,first[N],nxt[N],rank[N],rt;
inline void add(int u,int v){
	e[++cnt].u=u;e[cnt].v=v;e[cnt].w=0;
	nxt[cnt]=first[u];first[u]=cnt;
}
int dep[N],fa[N],w[N],siz[N],son[N];
inline void dfs1(int u,int f){
	fa[u]=f;
	dep[u]=dep[f]+1;
	siz[u]=1;
	for(int i=first[u];i;i=nxt[i]){
		int v=e[i].v;
		if(v==f)continue;
		w[v]=e[i].w;
		dfs1(v,u);
		siz[u]+=siz[v];
		if(siz[v]>siz[son[u]])son[u]=v;
	}
}
int top[N],id[N],a[N],num;
inline void dfs2(int x,int topx){
	id[x]=++num;
	a[num]=w[x];
	top[x]=topx;
	if(son[x])dfs2(son[x],topx);
	for(int i=first[x];i;i=nxt[i]){
		int v=e[i].v;
		if(v==fa[x]||x==son[x])continue;
		dfs2(v,v);
	}
}
int c[N<<1];
inline int lowbit(int x){return x&(-x);}
inline void update(int k,int val){
	while(k<=num){
		c[k]+=val;
		k+=lowbit(k);
	}
}
inline void add_range(int x,int y){
	while(top[x]!=top[y]){
		if(dep[top[x]]<dep[top[y]])swap(x,y);
		update(id[top[x]],1);
		update(id[x]+1,-1);
		x=fa[top[x]];
	}
	if(dep[x]>dep[y])swap(x,y);
	update(id[x]+1,1);
	update(id[y]+1,-1);
}
inline int query(int k){
	int ret=0;
	while(k){
		ret+=c[k];
		k-=lowbit(k);
	}
	return ret;
}
#define in read()
inline int read(){
	int k=1,x=0;
	char ch=getchar();
	while(ch>'9'||ch<'0'){
		if(ch=='-')k=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		x=x*10+ch-'0';
		ch=getchar();
	}
	return k*x;
}
int main(){
	freopen("P3038.in","r",stdin);
	freopen("P3038.ans","w",stdout);
	n=in;m=in;
	for(int i=1;i<n;i++){
		int u,v;
		u=in;v=in;
		rank[u]++;rank[v]++;
		add(u,v);
		add(v,u);
		if(rank[u]>rank[rt])rt=u;
		if(rank[v]>rank[rt])rt=v;
	}
	w[rt]=0;
	dfs1(rt,0);
	dfs2(rt,rt);
	for(int i=1;i<=num;i++){
		update(i,a[i]);
		update(i+1,-a[i]);
	}
	while(m--){
		char op;
		scanf(" %c",&op);
		int u=in,v=in;
		if(op=='P'){
			add_range(u,v);
		}
		else{
			if(dep[v]<dep[u])swap(u,v);
			printf("%d",query(id[v]));
		}
	} 
	return 0;
}