using malloc & realloc

Hi Everyone!
Is there a way to reduce the number of pointers used in this program using malloc itself.

Code:

---

#include<stdio.h>
#include<stdlib.h>
int main()
{
int *p,*q,i,*r,*w;
p=(int *)malloc(5*sizeof(int));
printf("Enter the 5 numbers\n");
q=p;
for(i=0;i<5;i++)
{
scanf("%d",p);
p++;
}
p=q;
r=(int *)realloc(q,8*sizeof(int));
w=r;
r+=5;
for(i=0;i<3;i++)
{
scanf("%d",r);
r++;
}
r=w;
for(i=0;i<8;i++)
{
printf("%d\n",*(int *)r);
r++;
}
p=q;
r=w;
free(r);
q=NULL;
w=NULL;
return 0;
}


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You could allocate 8 integers instead of only 5 and stop dicking around with realloc(), unless you're meant to show some competency with that function.

If you are, you have a potential leak. Here's how you handle it:

Code:

---

int *q = realloc( p, newSize * sizeof( *p ) );
if ( q != NULL ) {
  p = q;
}
else {
  free( p );
  p = NULL;
}

---

I was just experimenting with using malloc and realloac on how to access and see if it was reading into the new loaction,so took an example of 5 and 8.That's when I realised the number of pointers required to do this simple operation.

Well if it's a problem, you need to roll up your own functions to do this kind of stuff. If you think about it, a lot of this type of work is part of data structure management. So you need to do adequate planning and decide what functions you need to write. It'll be a lot easier if you can write it once, test, and forget about it.

You could also look for a library for a particular data structure. A lot of code is already written, you just have to find it.

ok.Thanks :)

hi.
The malloc() is used the create the memory allocation in dynamically.
and the realloc() is used the reallocating the memory for already exitsted memory in dynamically in C language.

Quote:

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Originally Posted by shruthi

Is there a way to reduce the number of pointers used in this program using malloc itself.

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You would only need two pointers: One which is always pointing to the start of your array and another "helper" pointer which does all the moving around.
Something like this:

Code:

---

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    int *numbers, *temp;
    int i;

    if ((numbers = malloc(5 * sizeof(*numbers))) == NULL)
    {
        fprintf(stderr, "Error allocating memory\n");
        exit(EXIT_FAILURE);
    }

    printf("Enter the 5 numbers\n");
    for(i = 0, temp = numbers; i < 5; i++, temp++)
        scanf("%d", temp);

    temp = realloc(numbers, 8 * sizeof(*numbers));
    if (temp != NULL)
        numbers = temp;
    else
    {
        fprintf(stderr, "Error reallocating memory\n");
        free(numbers);
        exit(EXIT_FAILURE);
    }

    printf("Enter 3 more numbers\n");
    for(i = 0, temp = numbers + 5; i < 3; i++, temp++)
        scanf("%d", temp);

    printf("The numbers: ");
    for(i = 0, temp = numbers; i < 8; i++, temp++)
        printf("%d ", *temp);
    putchar('\n');

    free(numbers);
    return EXIT_SUCCESS;
}

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Bye, Andreas

Quote:

---

Originally Posted by AndiPersti

You would only need two pointers: One which is always pointing to the start of your array and another "helper" pointer which does all the moving around.
Something like this:

Code:

---

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    int *numbers, *temp;
    int i;

    if ((numbers = malloc(5 * sizeof(*numbers))) == NULL)
    {
        fprintf(stderr, "Error allocating memory\n");
        exit(EXIT_FAILURE);
    }

    printf("Enter the 5 numbers\n");
    for(i = 0, temp = numbers; i < 5; i++, temp++)
        scanf("%d", temp);

    temp = realloc(numbers, 8 * sizeof(*numbers));
    if (temp != NULL)
        numbers = temp;
    else
    {
        fprintf(stderr, "Error reallocating memory\n");
        free(numbers);
        exit(EXIT_FAILURE);
    }

    printf("Enter 3 more numbers\n");
    for(i = 0, temp = numbers + 5; i < 3; i++, temp++)
        scanf("%d", temp);

    printf("The numbers: ");
    for(i = 0, temp = numbers; i < 8; i++, temp++)
        printf("%d ", *temp);
    putchar('\n');

    free(numbers);
    return EXIT_SUCCESS;
}

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Bye, Andreas

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This is great! Thanks :)