Dynamic programing with C++ problem in Hackerrank task

Recently I have been solving some hackerranks tasks.In advance I want to tell that I know basics of c++ (I read and made tasks from book "Programming: Principles and Practice Using C++") .. Unfortunately in one of these problem I got stuck and from few hours i can't move forward. When I tried to fix it, I experienced a bunch of runtime or segmentation errors. I know that errors are produced by my int** arrwhen program tries to modify it , but I can't figure out by what are caused. Also I aware that program can have more bugs which now i can't spot due to this first bad part of program. I know that further i program are more mistakes but now I focus on the first issue. I could write this program by using list or array but i want to challenge myself and do it with more low programing tools.

There is link to problem and below is my whole code

#include <vector>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <queue>
#include <stack>
#include <algorithm>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <limits>
#include <cstring>
#include <string>
#include <cassert>

using namespace std;
int N ,q;
int main()
{
   int lastAnswer=0;
   cin>>N>>q;
   int** arr = new int*[N];
   for(int i=0;i<N;i++)
   {
       arr[i]=nullptr;
   }
   for(int i=0; i<q;i++)
   {
       cout<<"it :"<<i<<", ";
       int a,b,c;
       cin>>a>>b>>c;
       cout<<"C:"<<c<<" ";
       int ind= (b^lastAnswer)%2;
       if(a==1){
          
               cout<<"{1: ";
               int* poi =arr[ind];
               cout<<"$arr[ind] ad:"<<arr[ind]<<" $";              
               int size =0;
               while(poi){poi++;size++;}
               cout<<" Size at beg:"<<size<<" $";
               int* n =new int[size+1];
               if(size!=0)
               {
                   for(int i=0; i<size;i++)
                       n[i]=poi[i];
                   for(int i=0; i<size+1;i++ )cout<<"i"<<i<<" "<<*poi<<" ";
                   delete[] poi;    
               }
               n[size]=c;
               cout<<" Elem n[size]:"<<c<<"  $";
               arr[ind] =n;
           cout<<"E:"<<*arr[ind]<<" for index:"<<ind<<" address:"<<arr[ind]<<'\n';
       }    
       else if(a==2)
       {
           cout<<"{2";
           int * ak = arr[ind];
           int size=0;
           while(ak)
           {
               ak++;size++;
           }
           lastAnswer = *arr[c%size];
           cout<<lastAnswer<<'\n';//only this cout is not debug
       }
               
       
       
   }

   
}

** I added added also debug code in this program.** For this input:

2 5
1 0 5
1 1 7
1 0 3
2 1 0
2 1 1

Output is:

it :0, C:5 {1: $arr[ind] ad:0 $Size at beg:0 $Elem n[size]:5  $E:5 for index:0 ads:0x1c8d5b0

it :1, C:7 {1: $arr[ind] ad:0 $Size at beg:0 $Elem n[size]:7  $E:7 for index:1 ad:0x1c8d4d0

it :2, C:3 {1: $arr[ind] ad:0x1c8d5b0 $Size at beg:0 $Elem n[size]:3  $E:3 for index:0 ad:0x1c8d410

it :3, 

Expected:

7

3

But without debug output, it doesn't print anything but shows "Runtime Error" which occurs after 3 iteration during getting from cin data I know that i should add delete or free function to prevent leak of memory but i think it would not change that i have error (or change my mind)

In advance thanks for your help :)