Dynamic Range Sum Queries

#include <bits/stdc++.h>
using namespace std;

void segmentTree(int ind, int low, int high, vector<long long> &seg, vector<long long> &inp) {
    if(low == high) {
        seg[ind] = inp[low];
        return;
    }
    int mid = (low + high) >> 1;
    segmentTree(2 * ind + 1, low, mid, seg, inp);
    segmentTree(2 * ind + 2, mid + 1, high, seg, inp);
    seg[ind] = seg[2 * ind + 1] + seg[2 * ind + 2];
}

void update(int ind, int low, int high, int pos, long long val, vector<long long> &seg) {
    if(low == high) {
        seg[ind] = val;
        return;
    }
    int mid = (low + high) >> 1;
    if(pos <= mid) update(2 * ind + 1, low, mid, pos, val, seg);
    else update(2 * ind + 2, mid + 1, high, pos, val, seg);
    seg[ind] = seg[2 * ind + 1] + seg[2 * ind + 2]; 
}

long long query(int ind, int low, int high, int l, int r, vector<long long> &seg) {
    if(high < l || low > r) return 0LL;
    if(low >= l && high <= r) return seg[ind];
    int mid = (low + high) >> 1;
    long long left = query(2 * ind + 1, low, mid, l, r, seg);
    long long right = query(2 * ind + 2, mid + 1, high, l, r, seg);
    return left + right;
}

void test_case() {
    int n, q;
    cin >> n >> q;
    vector<long long> inp(n);

    for(auto &a : inp) cin >> a;

    vector<long long> seg(4 * n);
    segmentTree(0, 0, n - 1, seg, inp);

    while(q--) {
        int type, l, r;
        cin >> type;
        if(type == 1) {
            int pos;
            long long val;
            cin >> pos >> val;
            pos--;
            update(0, 0, n - 1, pos, val, seg);
        } else {
            cin >> l >> r;
            l--;
            r--;
            cout << query(0, 0, n - 1, l, r, seg) << endl;
        }
    }
}

int main(){  
    int t = 1;
    // cin >> t;
    while(t--) test_case();
    return 0;
}