Shared code

#include<bits/stdc++.h>
using namespace std;
 
#define ll long long 
#define ar array 
 
const ll mod=1e9+7;
const ll mxN=2e5;
class segTree{
    ll N;
    vector<ll> st;
         
    public: segTree(ll n){
       N=n;
       st.resize(4*N+5);
    }

    void Build(vector<ll> a,ll node, ll L, ll R)
    {
        if (L == R)
        {
            st[node] = a[L];
            return;
        }
        ll M = (L + R) / 2;
        Build(a,node * 2 + 1, L, M);
        Build(a,node * 2 + 2, M + 1, R);
        st[node] = st[node * 2 + 1] + st[node * 2 + 2];
    }

    void Update(ll node, ll L, ll R, ll pos, ll val)
    {
        if (L == R)
        {
            st[node]= val;
            return;
        }
        ll M = (L + R) / 2;
        if (pos <= M)
            Update(node * 2+1, L, M, pos, val);
        else
            Update(node * 2 + 2, M + 1, R, pos, val);

        st[node] = st[node * 2+1]+st[node * 2 + 2];
    }

    ll Query(ll node, ll L, ll R, ll i, ll j)
    {
        if (j < L || i > R)
            return 0;
        if (i <= L && R <= j)
            return st[node];
        ll M = (L + R) / 2;
        return Query(node * 2+1, L, M, i, j) + Query(node * 2 + 2, M + 1, R, i, j);

    }
};

//tree
vector<ll> adj[mxN];
//weight of each node
ll val[mxN];
//dp[i][0] -> will store the in-time of ith node 
//dp[i][1] -> will store the out-time of ith node
ll dp[mxN][2];
//time
ll t;
//flattened tree
vector<ll> a;

void dfs(ll u=0,ll p=-1){
    dp[u][0]=t;
    a.push_back(val[u]);

    for(auto v:adj[u]){
        if(v==p)continue;
        t++;
        dfs(v,u);
    }
    dp[u][1]=t;
}
void solve()
{
    ll n,q;cin>>n,cin>>q;
    for(ll i=0;i<n;i++)
        cin>>val[i];

    for(ll i=0;i<n-1;i++){
        ll p,q;cin>>p>>q,--p,--q;
        adj[p].push_back(q);
        adj[q].push_back(p);
    }
    t=0;
    dfs();

    segTree st1(a.size());
    st1.Build(a,0,0,n-1);
    while(q--){
        ll x;cin>>x;
        if(x==1){
            ll node,value;cin>>node>>value;
            --node;
            st1.Update(0,0,n-1,dp[node][0],value);
        }
        else{
            ll node;cin>>node;
            --node;
            cout<<st1.Query(0,0,n-1,dp[node][0],dp[node][1])<<"\n";
        }

    }
    

    
}
int main()
{
    solve();
    return 0;
}