CODEWITHSUNDEEP
c
laura
laura

Reputation: 2135

double dimensional array as return value

For my homework, I have to read data from an input file and to store it in a double dimensional array and then pass this array to another function. This is what I have tried so far, but I don't know when I call this function in main it gives the error:

Access violation writing location 0x00000000.

I have tried to dynamically allocate memory and it gives the same error. What I am doing wrong?

The last update of the code:

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

int *a[2];
void getData(void)
{
    FILE *fp = fopen("input.txt", "r");
    int number;

    fscanf(fp, "%d", &number);


    for (int i = 0; i < number; i++)
    {
        a[i]=(int*)malloc(number * sizeof (int));
        fscanf(fp, "%d %d", &a[i][0], &a[i][1]);
    }
    fclose(fp);
}


int main()
{   
    getData();
    for(int i=0;i<8;i++)
    {
        printf("%d %d\n",a[i][0],a[i][1]);
    }
}

Upvotes: 4

Views: 162

Answers (2)

md5
md5

Reputation: 23699

You are not allocating the first dimension, ie a is a null pointer when you are trying to dereference it.

#include <stdlib.h>
a = malloc(number * sizeof *a);

BTW, sizeof(int) is not sufficient to store two numbers.

#include <stdlib.h>
a[i] = malloc(2 * sizeof *a[i]); 
fscanf(iFile, "%d %d", &a[i][0], &a[i][1]);

Here is a whole correct code (although not perfect, as long as a is an hugly global variable):

int (*a)[2] = NULL;

void getData(void)
{
    FILE *fp = fopen("input.txt", "r");
    int number;

    fscanf(fp, "%d", &number);
    a = malloc(number * sizeof *a);

    for (int i = 0; i < number; i++)
        fscanf(fp, "%d %d", &a[i][0], &a[i][1]);

    fclose(fp);
}

Upvotes: 1

user93353
user93353

Reputation: 14039

You need to allocate memory for a

Before the for loop

a = (int **)malloc(number * sizeof(int *))

Upvotes: 5

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