Variable Sized Arrays Hackerrank

VariableSizedArrays.cpp

// See question: https://hackerrank-challenge-pdfs.s3.amazonaws.com/14507-variable-sized-arrays-English?AWSAccessKeyId=AKIAJ4WZFDFQTZRGO3QA&Expires=1537933597&Signature=hih3xrYn04RUlnsFKRVP1%2BFTgWA%3D&response-content-disposition=inline%3B%20filename%3Dvariable-sized-arrays-English.pdf&response-content-type=application%2Fpdf

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    int n, q;
    cin >> n >> q;
    
    vector<vector<int>> v(n);

    for (int i = 0; i < n; i++) 
    {
        int k;
        cin >> k;

        v[i].resize(k);
        for (int j = 0; j < k; j++) {
            cin >> v[i][j];
        }
    }

    for (int num = 0; num < q; num++) {
        int i, j;
        cin >> i >> j;
        cout << v[i][j] << endl;
    }

    return 0;
}