Difference Array: Basic

#include <bits/stdc++.h>

using namespace std;

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

vector<int> findDiffsArray(const vector<int>& arr) {
    int n = arr.size();
    vector<int> diffs(n - 1);
    for (int i = 0; i < n - 1; i++) {
        diffs[i] = arr[i + 1] - arr[i];
    }
    return diffs;
}

vector<int> precalc(vector<int> b) {
    b.insert(b.begin(), 0); // add leading zero
    vector<int> a = findDiffsArray(b);
    return a;
}

vector<int> postcalc(const vector<int>& a) {
    vector<int> finalB = findPrefixSums(a);
    finalB.erase(finalB.begin()); // delete leading zero
    return finalB;
}

int main() {
    int n;
    cin >> n;
    vector<int> b(n);
    for (int &val : b) {
        cin >> val;
    }
    vector<int> diffArr = precalc(b);

    auto addOnHalfInterval = [&](int left, int right, int d) { // [left, right) += d
        diffArr[left] += d;
        if (right < n) {
            diffArr[right] -= d;
        }
    };

    int queriesNumber;
    cin >> queriesNumber;
    for (int i = 0; i < queriesNumber; i++) {
        int l, r;
        int d;
        cin >> l >> r >> d;
        l--;
        addOnHalfInterval(l, r, d);
    }
    vector<int> finalB = postcalc(diffArr);
    for (int val : finalB) {
        cout << val << ' ';
    }
    cout << endl;
    return 0;
}