Question

For my homework it is given one dimensional array and i have to convert it in a two dimensional array. The two dimensional array has 2 for the number of columns, because i have to represent the one dimensional array as pairs(the value of the number, the number of appearences in the array).
This is what have tried. The error appears on the last 2 lines of code: access violation writing location 0xfdfdfdfd.

#include <iostream>
#include <stdlib.h>
using namespace std;

int main()
{
    const int NR=17;
    int arr[NR]={6,7,3,1,3,2,4,4,7,5,1,1,5,6,6,4,5};
    int **newArr;
    int count=0;
    int countLines=0;
    int searched;
    for(int i=0;i<NR;i++)
    {
            newArr=new int*[countLines];
        for(int i=0;i<countLines;i++)
        {
            newArr[i]=new int[2];
        }
        searched=arr[i];
        if(i>0)
        {
            for(int k=0;k<countLines;k++)
            {
                if(newArr[countLines][0] == searched)
                {
                    searched=arr[i]++;
                }

                for(int j=0;j<NR;j++)
                {
                    if(searched==arr[j])
                    {
                        count++;
                    }
                }
                countLines++;
            }
        }
        else
        {
            for(int j=0;j<NR;j++)
            {
                if(searched==arr[j])
                {
                    count++;
                }
            }
            countLines++;
        }

        newArr[countLines][0]=searched;
        newArr[countLines][1]=count;
    }
}

Answer 1

First you are using newArr in the first loop before allocating it any memory. You cannot dereference a pointer which owns no legal memory. It results in undefined behavior.

Secondly in the last part, you are allocating newArr a memory equal to countLines thus.

newArr = new int*[countLines] ;

It means that the indices in the first dimension of newArr are 0------>countLines-1. Doing newArr[countLines][0] = searched ; is again undefined. Make it newArr[countLines - 1].