array 2 dimension using pointer and function in c

[riandrp]

i stuck with my code to change this code by using a pointer. mybe someone want to help me fixed it.

this my code :

#include <stdio.h>
#define size 100


int array2d(int x[size][size], int a, int b)
{
    int i, j;
    for (i = 0; i < a; i++)
    {
        for (j = 0; j < b; j++)
        {
            printf("%d ", x[i][j]);
        }
        printf("\n");
    }
}
int main()
{
    int a, b;
    int x[size][size];


    printf("enter the size of array (row) & (column) : ");
    scanf("%d %d", &a, &b);


    printf("enter the number : ");


    for (int i = 0; i < a; i++) //reading input
    {
        for (int j = 0; j < b; j++)
        {
            scanf("%d", &x[i][j]);
        }
    }


    array2d(x, a, b);


    return 0;
}

please help me

this code input :
2 2

and
1 2 3 4

should be an output :
1 2
3 4

[hamster_nz]

It does:

$ ./main 
enter the size of array (row) & (column) : 2 2
enter the number : 1 2 3 4
1 2 
3 4 
$

Do you still have a problem?

[riandrp]

yes i have problem to add a pointer in there

[Salem]

What do you mean - add pointer?

You can make a 1-line change of

int array2d(int (*x)[size], int a, int b)

Does that count?

If you were looking for

int array2d(int **x, int a, int b)

then that's rather more work in main.

int **x;
x = malloc( a * sizeof(*x));
for ( i = 0 ; i < a ; i++ ) x[i] = malloc( b*sizeof(*x[i]));

[riandrp]

can you help me to write a complete code using a poniter from the code that i have created

[Salem]

Erm, that's all you needed to do.

#include <stdio.h>
#include <stdlib.h>
#define size 100


int array2d(int **x, int a, int b)
{
    int i, j;
    for (i = 0; i < a; i++)
    {
        for (j = 0; j < b; j++)
        {
            printf("%d ", x[i][j]);
        }
        printf("\n");
    }
}
int main()
{
    int a, b;
//    int x[size][size];
    int **x;


    printf("enter the size of array (row) & (column) : ");
    scanf("%d %d", &a, &b);

    x = malloc( a * sizeof(*x));
    for ( int i = 0 ; i < a ; i++ ) x[i] = malloc( b*sizeof(*x[i]));

    printf("enter the number : ");


    for (int i = 0; i < a; i++) //reading input
    {
        for (int j = 0; j < b; j++)
        {
            scanf("%d", &x[i][j]);
        }
    }


    array2d(x, a, b);


    return 0;
}

[Malcolm McLean]

Most beginners' C books introduce 2D arrays iimmediately after 1D arrays.

This is a mistake. Multidimensional arrays were historically not implemented well in C, and should be thought of as an advanced feature. The situation is a bit better with the latest versions of C, but these are not supported everywhere.

What most C programmers do is to pass buffers for naturally 2D data such as images. The buffer is then accessed using the formula buffer[y*width+x]. It's not less efficient as the compiler will do that underlying calculation anyway. And it makes it easy to have arrays with dimensions determined at runtime.

[riandrp]

thank you