difference array technique implementation

difference_array.cpp

/**
	* @param a - initial array
	* @param query - query array - [li, ri, xi], li and ri are zero-based indexed
	* @return array after processing all queries
 */
vector<int> HandleRangeUpdateQuery (vector<int> a, vector<vector<int>> query) {
	// creating another array to handle queries
	vector<int> b (a.size() + 1, 0);

	for (auto& q : query) {
		int l = q[0], r = q[1], x = q[2];
		// handling query
		b[l] += x;
		b[r + 1] -= x;
	}

	// calculating prefix sum of the array b
	for (int i = 1; i < b.size() - 1; i += 1) {
		b[i] += b[i - 1];
	}

	// adding all updates back to original array a
	for (int i = 0; i < a.size(); i += 1) {
		a[i] += b[i];
	}

	return a;
}