Question

Below is part of my code to sort table of x,y,z cordinates using x,y with qsort. I can read all the data into *xyz part of the structure and allocate memory, I keep getting errors on line 7, "read access violation". I would take any help...Thanks

typedef struct

{

       int x;

       int y;

       int z;

} Coordinates;

typedef Coordinates * xyz;

int compare(const void *p1, const void *p2)

       {

       const xyz num1 = *(const xyz *)p1;

       const xyz num2 = *(const xyz *)p2;

7      if (num1->x < num2->x)    //read access violation

       {

              return -1;

       }

       else if (num1->x > num2->x)

       {

              return 1;

       }

       else

       {

              if (num1->y < num2->y)

              {

                     return -1;

              }

              else if (num1->y > num2->y)

              {

                     return 1;

              }

              else

              {

                     return 0;

              }

       }

Main

{

//allocates memory

Coordinates * xyz = (Coordinates *) malloc(sizeof(Coordinates) * numElem);

qsort(xyz, numElem, sizeof(xyz), compare);

}

Answer 1

If you have any doubts, please give me comment...

#include <stdio.h>

#include <stdlib.h>

typedef struct

{

    int x;

    int y;

    int z;

} Coordinates;

int compare(const void *p1, const void *p2)

{

    const Coordinates *num1 = (const Coordinates *)p1;

    const Coordinates *num2 = (const Coordinates *)p2;

    if (num1->x < num2->x) //read access violation

    {

        return -1;

    }

    else if (num1->x > num2->x)

    {

        return 1;

    }

    else

    {

        if (num1->y < num2->y)

        {

            return -1;

        }

        else if (num1->y > num2->y)

        {

            return 1;

        }

        else

        {

            return 0;

        }

    }

}

int main()

{

    //allocates memory

    Coordinates *xyz = (Coordinates *)malloc(sizeof(Coordinates) * numElem);

    

    qsort(xyz, numElem, sizeof(Coordinates), compare);

    return 0;

}