#include<bits/stdc++.h>
using namespace std;
int n,q;
int w[100005],c[100005];
vector<int>adj[100005];
int siz[100005],dfn[100005],fa[100005],dep[100005];
int hson[100005],top[100005],counter;
int root[100005];
struct Node {
	int l,r;
	int maxi,sum;
} tree[20000005];
void add(int l,int r,int pos,int x,int &rt) {
	if(!rt)rt = ++counter;
	tree[rt].maxi = max(tree[rt].maxi,x);
	tree[rt].sum += x;
	int mid = (l+r)>>1;
	if(l == r) {
		return ;
	} else if(mid>=pos) {
		add(l,mid,pos,x,tree[rt].l);
	} else {
		add(mid+1,r,pos,x,tree[rt].r);
	}
}
void del(int l,int r,int pos,int &rt) {
	if(l == r) {
		tree[rt].maxi = tree[rt].sum = 0;
		return ;
	}
	int mid = (l+r)>>1;
	if(mid>=pos) {
		del(l,mid,pos,tree[rt].l);
	} else {
		del(mid+1,r,pos,tree[rt].r);
	}
	tree[rt].maxi = max(tree[tree[rt].l].maxi,tree[tree[rt].r].maxi);
	tree[rt].sum = tree[tree[rt].l].sum+tree[tree[rt].r].sum;
}
int query(int l,int r,int ql,int qr,int rt,int op) {
	if(l>qr||r<ql) {
		return 0;
	} else if(l>=ql&&r<=qr) {
		if(op == 1) {
			return tree[rt].sum;
		} else {
			return tree[rt].maxi;
		}
	}
	int mid = (l+r)>>1;
	if(op == 1)return query(l,mid,ql,qr,tree[rt].l,op)+query(mid+1,r,ql,qr,tree[rt].r,op);
	else return max(query(l,mid,ql,qr,tree[rt].l,op),query(mid+1,r,ql,qr,tree[rt].r,op));
}
int Query(int x,int y,int col,int op) {
	int result = 0;
	while(top[x] != top[y]) {
		if(dep[top[x]]<dep[top[y]]) {
			swap(x,y);
		}
		if(op == 1) {
			result += query(1,n,dfn[top[x]],dfn[x],root[col],op);
		} else {
			result = max(result,query(1,n,dfn[top[x]],dfn[x],root[col],op));
		}
		x = fa[top[x]];
	}
	if(dep[x]<dep[y])swap(x,y);
	if(op == 1) {
		result += query(1,n,dfn[y],dfn[x],root[col],op);
	} else {
		result = max(result,query(1,n,dfn[y],dfn[x],root[col],op));
	}
	return result;
}
void DFS1(int cur,int lst) {
	siz[cur] = 1;
	dep[cur] = dep[lst]+1;
	fa[cur] = lst;
	for(auto x : adj[cur]) {
		if(x == lst) continue;
		DFS1(x,cur);
		siz[cur] += siz[x];
		if(siz[x]>siz[hson[cur]]) {
			hson[cur] = x;
		}
	}
}
void DFS2(int cur,int st) {
	top[cur] = st;
	dfn[cur] = ++counter;
	if(hson[cur] != 0) {
		DFS2(hson[cur],st);
	}
	for(auto x : adj[cur]) {
		if(x == hson[cur]||x == fa[cur]) continue;
		DFS2(x,x);
	}
}
int main() {
	cin>>n>>q;
	for(int i = 1; i <= n; i++) {
		scanf("%d %d",&w[i],&c[i]);
	}
	for(int i = 0; i<n-1; i++) {
		int u,v;
		scanf("%d %d",&u,&v);
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	DFS1(1,0);
	DFS2(1,1);
	counter = 0;
	for(int i = 1; i <= n; i++) {
		add(1,n,dfn[i],w[i],root[c[i]]);
	}

	while(q--) {
		char op[2];
		int x,y;
		cin>>op>>x>>y;
		if(op[1] == 'C') {
			del(1,n,dfn[x],root[c[x]]);
			add(1,n,dfn[x],w[x],root[y]);
			c[x] = y;
		} else if(op[1] == 'W') {
			del(1,n,dfn[x],root[c[x]]);
			add(1,n,dfn[x],y,root[c[x]]);
			w[x] = y;
		} else if(op[1] == 'S') {
			printf("%d\n",Query(x,y,c[x],1));
		} else {
			printf("%d\n",Query(x,y,c[x],2));
		}
	}
}

同样一份代码，使用 C++ 20 评测输出 $0$，但是使用 C++ 17 通过了（）