Prefix Sums: Structs

#include <bits/stdc++.h>

using namespace std;

struct SegmentSumStructure {
    vector<int> prefixSums;

    SegmentSumStructure(const vector<int>& a) {
        int n = a.size();
        prefixSums.assign(n + 1, 0);
        for (int i = 0; i < n; i++) {
            prefixSums[i + 1] = prefixSums[i] + a[i];
        }
    }

    int findSum(int left, int right) { // [left; right)
        return prefixSums[right] - prefixSums[left];
    }

};

int main() {
    int n;
    cin >> n;
    vector<int> arr(n);
    for (int& val : arr) {
        cin >> val;
    }
    SegmentSumStructure myAdder(arr);

    int queriesNumber;
    cin >> queriesNumber;
    for (int i = 0; i < queriesNumber; i++) {
        int left, right;
        cin >> left >> right;
        left--;
        cout << myAdder.findSum(left, right) << '\n';
    }
    return 0;
}