树剖太难调了

#include <bits/stdc++.h>
#define int long long

#define min(x, y) (x < y ? x : y)

#define max(x, y) (x > y ? x : y)

#define lowbit(x) (x & -x)

using namespace std;
const int DM[8][2] = {0, 1, 0, -1, 1, 0, -1, 0, 1, 1, 1, -1, -1, 1, -1, -1};
const int HASHMOD = 9223372036854775783;
const int HASHBASE = 131;
const int HASHITEM = 999997;
const int N = 100001;
vector<int> e[N];
int num[N], fa[N], hvy[N], rev[N], seg[N], son[N], top[N], dep[N];
struct Edge
{
    int u, v, d, sto;
} edg[N];
int tree[4 * N + 1];
void init1(int u, int f)
{
    son[u] = 1;
    fa[u] = f;
    dep[u] = dep[f] + 1;
    for (auto v : e[u])
    {
        if (v == f)
        {
            continue;
        }
        init1(v, u);
        son[u] += son[v];
        if (son[v] > son[hvy[u]])
        {
            hvy[u] = v;
        }
    }
}
void init2(int u, int fa)
{
    if (hvy[u])
    {
        int v = hvy[u];
        seg[v] = ++seg[0];
        rev[seg[0]] = v;
        top[v] = top[u];
        init2(v, u);
    }
    for (auto v : e[u])
    {
        if (top[v] || v == fa)
            continue;
        seg[v] = ++seg[0];
        rev[seg[0]] = v;
        top[v] = v;
        init2(v, u);
    }
}
void pushup(int k)
{
    tree[k] = max(tree[k << 1], tree[k << 1 | 1]);
}
void build(int k, int l, int r)
{
    if (l == r)
    {
        tree[k] = num[rev[l]];
        return;
    }
    int mid = (l + r) >> 1;
    build(k << 1, l, mid);
    build(k << 1 | 1, mid + 1, r);
    pushup(k);
}
void change(int k, int l, int r, int x, int v)
{
    if (l == r)
    {
        tree[k] = v;
        return;
    }
    int mid = (l + r) >> 1;
    if (x <= mid)
    {
        change(k << 1, l, mid, x, v);
    }
    else
    {
        change(k << 1 | 1, mid + 1, r, x, v);
    }
    pushup(k);
}
int query(int k, int l, int r, int x, int y)
{
    if (x <= l && r <= y)
    {
        return tree[k];
    }
    int mid = (l + r) >> 1, res = -LLONG_MAX;
    if (x <= mid)
    {
        res = max(res, query(k << 1, l, mid, x, y));
    }
    if (y > mid)
    {
        res = max(res, query(k << 1 | 1, mid + 1, r, x, y));
    }
    return res;
}
int qry_max(int x, int y)
{
    if (top[x] != top[y])
    {
        if (dep[top[x]] < dep[top[y]])
        {
            swap(x, y);
        }   
        return max(qry_max(fa[top[x]], y), query(1, 1, seg[0], seg[top[x]], seg[x]));
    }
    if (dep[y] < dep[x])
    {
        swap(x, y);
    }
    if (x == y)
    {
        return 0;
    }
    return query(1, 1, seg[0], seg[x] - 1, seg[y]);
}
signed main()
{
    int n;
    cin >> n;
    for (int i = 1; i < n; i++)
    {
        int u, v, d;
        cin >> u >> v >> d;
        e[u].push_back(v);
        e[v].push_back(u);
        edg[i] = {u, v, d, 0};
    }
    top[1] = 1;
    seg[1] = ++seg[0];
    rev[1] = 1;
    init1(1, 0);
    for (int i = 1; i <= n; i++)
    {
        if (fa[edg[i].u] == edg[i].v)
        {
            edg[i].sto = edg[i].u;
            num[edg[i].u] = edg[i].d;
        }
        else
        {
            edg[i].sto = edg[i].v;
            num[edg[i].v] = edg[i].d;
        }
    }
    init2(1, 0);
    build(1, 1, n);
    // cout << query(1, 1, n, 1, n, 1);
    string opt;
    while (1)
    {
        cin >> opt;
        if (opt == "DONE")
        {
            break;
        }
        int x, y;
        cin >> x >> y;
        if (opt == "CHANGE")
        {
            change(1, 1, n, seg[edg[x].sto], y);
        }
        if (opt == "QUERY")
        {
            if (x == y)
            {
                cout << 0 << '\n';
            }
            else
            {
                cout << qry_max(x, y) << '\n';
            }
        }
    }
}