Path Queries - Euler Tour Technique - CSES

//Make CSP great again
#include <bits/stdc++.h>
#define TASK "TESTCODE"
using namespace std;
const int N = 2e5;
int n, a[N + 1], q;
vector<int> Adj[N + 1];
struct FenwickTree
{
    long long b1[N + 1], b2[N + 1];
    void add(long long b[], int pos, long long val)
    {
        for (; pos <= n; pos += pos & (-pos))
        {
            b[pos] += val;
        }
    }
    void add_range(int l, int r, long long x)
    {
        add(b1, l, x);
        add(b1, r + 1, -x);
        add(b2, l, x * (l - 1));
        add(b2, r + 1, -x * r);
    }
    long long sum(long long b[], int pos)
    {
        long long ret = 0;
        for (; pos > 0; pos -= pos & (- pos))
        {
            ret += b[pos];
        }
        return ret;
    }
    long long prefix(int pos)
    {
        return sum(b1, pos) * pos - sum(b2, pos);
    }
    long long sum_range(int l, int r)
    {
        return prefix(r) - prefix(l - 1);
    }
};
FenwickTree Tree;
void read()
{
    cin >> n >> q;
    for (int i = 1; i <= n; ++ i)
    {
        cin >> a[i];
    }
    for (int i = 1; i < n; ++ i)
    {
        int u, v;
        cin >> u >> v;
        Adj[u].push_back(v);
        Adj[v].push_back(u);
    }
}
int st[N + 1], ed[N + 1], timer = 0;
void DFS(int u, int p)
{
    ++timer;
    st[u] = timer;
    for (int v : Adj[u])
    {
        if (v != p)
        {
            DFS(v, u);
        }
    }
    ed[u] = timer;
}
void solve()
{
    DFS(1, 0);
    for (int i = 1; i <= n; ++ i)
    {
        Tree.add_range(st[i], ed[i], 1LL * a[i]);
    }
    while(q--)
    {
        int t;
        cin >> t;
        if (t == 1)
        {
            int u, x;
            cin >> u >> x;
            Tree.add_range(st[u], ed[u], x - a[u]);
            a[u] = x;
        }
        else
        {
            int u;
            cin >> u;
            cout << Tree.sum_range(st[u], st[u]) << '\n';
        }
    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (fopen(TASK".INP", "r"))
    {
        freopen(TASK".INP", "r", stdin);
        //freopen(TASK".OUT", "w", stdout);
    }
    int t = 1;
    bool typetest = false;
    if (typetest)
    {
        cin >> t;
    }
    for (int __ = 1; __ <= t; ++ __)
    {
        read();
        solve();
    }
}