请求大佬救援，线段树合并模板题

#include<bits/stdc++.h>
using namespace std;
#define N 200010
int n, m, ans[N];
int tmp=0, head[N];
int sum[N<<2], ls[N<<2], rs[N<<2], c[N<<2];
struct edge{
    int to, next;
}e[N<<4];
void add(int u, int v){
    e[++tmp] = (edge){v, head[u]};
    head[u] = tmp;
}
int node=0, root[N], d[N], siz[N], fa[N], son[N];
void dfs1(int x, int f){//树链剖分准备求LCA
    d[x] = d[f]+1;
    fa[x] = f;
    siz[x] = 1;
    for(int i=head[x]; i; i=e[i].next){
        int y=e[i].to;
        if(y == f) continue;
        dfs1(y, x);
        siz[x] += siz[y];
        if(!son[x || siz[son[x]]<siz[y]])
            son[x] = y;
    }
}
int cnt=0, id[N], tp[N];
void dfs2(int x, int top){
    id[++cnt] = x;
    tp[x] = top;
    if(!son[x]) return ;
    dfs2(son[x], top);
    for(int i=head[x]; i; i=e[i].next){
        int y=e[i].to;
        if(y==fa[x] || y==son[x]) continue;
        dfs2(y, y);
    }
}
int LCA(int x, int y){
    while(tp[x] != tp[y]){
        if(d[tp[x]] < d[tp[y]]) swap(x, y);
        x = fa[tp[x]];
    }
    return d[x]<d[y]?x:y;
}
void pushup(int p){//当前节点货物最多 = max(左儿子最多, 右儿子最多)
    if(sum[ls[p]] >= sum[rs[p]]){//等于号钦定了当个数相同时输出小的，权值线段树越左边越小
        sum[p] = sum[ls[p]];
        c[p] = c[ls[p]];
    }
    else{
        sum[p] = sum[rs[p]];
        c[p] = c[rs[p]];
    }
    return ;
}
void modify(int &p, int l, int r, int pos, int val){
    if(!p) p=++node;//动态开点
    if(l==r){
        sum[p]+=val;
        if(sum[p]!=0) c[p]=l;
        return ;
    }
    int mid = l+r>>1;
    if(pos<=mid) modify(ls[p], l, mid, pos, val);
    if(pos>mid) modify(rs[p], mid+1, r, pos, val);
    pushup(p);
    return ;
}
int merge(int x, int y, int l, int r){
    if(!x || !y) return x+y;
    if(l == r){
        sum[x] += sum[y];
        if(sum[x]!=0) c[x] = l;
        return x;
    }
    int mid = l+r>>1;
    ls[x] = merge(ls[x], ls[y], l, mid);
    rs[x] = merge(rs[x], rs[y], mid+1, r);
    pushup(x);
    return x;
}
void calc(int x){
    for(int i=head[x]; i; i=e[i].next){
        int y = e[i].to;
        if(y==fa[x]) continue;
        calc(y);
        root[x] = merge(root[x], root[y], 1, N);
    }
    if(sum[root[x]]==0) ans[x]=0;
    else ans[x] = c[root[x]];
    return ;
}
int main()
{
    //freopen("P4556.in", "r", stdin);
    //freopen("P4556.out", "w", stdout);
    scanf("%d%d", &n, &m);
    for(int i=1; i<=n-1; i++){
        int u, v;
        scanf("%d%d", &u, &v);
        add(u, v); add(v, u);
    }
    dfs1(1, 0);
    dfs2(1, 1);
    //对于原图的每一个节点,都建一棵权值线段树
    while(m--){
        int x, y, z;
        scanf("%d%d%d", &x, &y, &z);
        int lca = LCA(x, y);
        modify(root[x], 1, N, z, 1);
        modify(root[fa[lca]], 1, N, z, -1);
        if(x!=y){
            modify(root[y], 1, N, z, 1);
            modify(root[lca], 1, N, z, -1);
        }//树上差分的技巧, 最终的答案是当前节点整个子树的权值线段树合并起来后再算最多粮食种类
    }
    calc(1);
    for(int i=1; i<=n; i++) printf("%d\n", ans[i]);
    return 0;
}