We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
  1. Prepare
  2. C++
  3. Introduction
  4. Variable Sized Arrays
  5. Discussions

Variable Sized Arrays

  • a_stewart_au
     + 44 comments

    The Problem tells you everything you need to know to answer the question. You just have to read closely.

    Here is my solution with added comments. I've used a raw array of arrays, dynamically allocated and via pointers, so they must be manually deleted afterwards. I could have also used a std::vector, but the question does say 'array'.

    #include <iostream>

using namespace std;

int main() {
	// get length of 2D array and number of queries
	int n, q;
	cin >> n >> q;

	// create 2D array
	int** a = new int*[n]();

	// fill 2D array with 1D subarrays
	for (int i = 0; i < n; i++) {
		// get the length of the 1D array at a[i]
		int k;
		cin >> k;

		// create the 1D subarray with the given length
		int* i_arr = new int[k]();

		// fill the subarray with k values
		for (int j = 0; j < k; j++) {
			cin >> i_arr[j];
		}

		// store the subarray in a
		a[i] = i_arr;
	}


	// run queries on a
	for (int q_num = 0; q_num < q; q_num++) {
		// get i, j as the 'query' to get a value from a
		int i, j;
		cin >> i >> j;
		cout << a[i][j] << endl;
	}

	// delete 2D array (each subarray must be deleted)
	for (int i = 0; i < n; i++) {
		delete[] a[i];
	}
	delete[] a;

	return 0;
}

    OR with std::vector:

    #include <iostream>
#include <vector>

using namespace std;

int main() {
	// get length of array 'a' and number of queries
	int n, q;
	cin >> n >> q;

	// create vector of vectors
	vector<vector<int>> a(n);

	// fill each 2D vector i with k_i values
	for (int i = 0; i < n; i++) {
		// get the length k of the vector at a[i]
		int k;
		cin >> k;

		// fill the vector with k values
		a[i].resize(k);
		for (int j = 0; j < k; j++) {
			cin >> a[i][j];
		}
	}

	// run queries on a
	for (int q_num = 0; q_num < q; q_num++) {
		// get i, j as the 'query' to get a value from a
		int i, j;
		cin >> i >> j;
		cout << a[i][j] << endl;
	}

	return 0;
}