Hackerrank C++ Variable Sized Arrays challenge

varSizeArray.cpp

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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n;
    int q;
    cin >> n >> q;
    vector<int> a[n];
    for(int i = 0; i < n; i++){
        int m;
        cin >> m;
        int o;
        for(int j = 0; j < m; j++){
            cin >> o;
            a[i].push_back(o);
        }
    }
    
    int r, s;
    for(int k = 1; k <= q; k++){
        cin >> r >> s;
        cout << a[r][s] << endl;
    }
    return 0;
}

`
#include
#include

using namespace std;

int main() {
int numOfArrays, numOfQueries;

cin >> numOfArrays >> numOfQueries;

int arrayIndexes[100000];
int elementIndexes[100000];
int board[numOfArrays][300000];

for(int i = 0; i < numOfArrays; i++){
    int limit;
    cin >> limit;
    for(int j = 0; j < limit; j++){
        cin >> board[i][j];
    }
}

for(int l = 0; l < numOfQueries; l++){
    int arrayIn, elementIn;
    cin >> arrayIn >> elementIn;
    arrayIndexes[l] = arrayIn;
    elementIndexes[l] = elementIn;
}

for(int j = 0; j < numOfQueries; j++){
    int currentArr = arrayIndexes[j], currentElement = elementIndexes[j];
    cout << board[currentArr][currentElement] << endl;
}
return 0;

}
`
I get segmentation fault myself, does anyone know what exactly is wrong with my code?

You are getting a segmentation fault.
Segmentation fault occurs when you are trying to access memory which you dont own, consequently to prevent memory from getting corrupted and unusable C++ has a built-in mechanism to prevent this, which raises the SegFault/Segmentation Fault/Core dump.

to prevent this from occurring try breaking you problem into parts and converting your code in different 'functions'.

this may seem primitive but if anyone has an expert solution, im all ears.

EDIT: A vector can also resolve this.