Converting 2D array to 1D in C

Question

I created a 2d array where the user can write the size (column and row) and fill it with random numbers, but I am having trouble converting from 2d to 1d. My question is how can i convert 2d array to 1d(like i am creating 3x3 array like this 92 88 4 next line 6 10 36 next line 96 66 83 and i want to convert it like 92 88 4 6 10 36 96 66 83). And if there is a problem with my code, please tell me. (Sorry for my grammatical errors)

This is my code;

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

int main(void)
{
    printf("Enter the number of rows: ");
    int i; 
    scanf("%d", &i);

    printf("Enter the number of columns: ");
    int y; 
    scanf("%d", &y);

    int array[i][y];
    int rows, columns;
    int random;

    srand((unsigned)time(NULL));

    for(rows=0;rows<i;rows++)
        {
            for(columns=0;columns<y;columns++)
                {
                    random=rand()%100+1;

                    array[rows][columns] = random;
                    printf("%i\t",array[rows][columns]);
                }

            printf("\n");
        }

return 0;
}

Answer 1

#include <stdio.h>

int main()
{
    int i = 0;
    int a[3][3] = {{92,88,4},{6,10,36},{96,66,83}};
    int *b;
    b=&a[0][0];
    for(i=0; i< 9; i++){
      printf("%d\t", b[i]);
    }
    return 0;
 }

This works because in C/C++ multidimensional arrays are stored continuously in memory. A good discussion could be found here

Answer 2

Firstly, for time function in srand((unsigned)time(NULL)); you need to include <time.h> .

For storing value in 1D array, you just create an array with size = col * row . In this example below, i allocate the int pointer for saving all the values:

int * arr_1D = malloc(sizeof(int) * i * y);
    if (arr_1D == NULL)
        exit(-1);

The complete code for you (i just added something for convering 2D to 1D):

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

int main(void)
{
    printf("Enter the number of rows: ");
    int i; 
    scanf("%d", &i);

    printf("Enter the number of columns: ");
    int y; 
    scanf("%d", &y);

    int array[i][y];
    int rows, columns;
    int random;

    srand((unsigned)time(NULL));

    int * arr_1D = malloc(sizeof(int) * i * y);
    if (arr_1D == NULL)
        exit(-1);

    int count = 0;
    for(rows=0;rows<i;rows++)
        {
            for(columns=0;columns<y;columns++)
                {
                    random=rand()%100+1;

                    array[rows][columns] = random;
                    printf("%i\t",array[rows][columns]);
                    // The code for converting 2D to 1D array 
                    arr_1D[count++] =  array[rows][columns];
                }

            printf("\n");
        }

    for (int k = 0; k < count; ++k)
    {
        printf("%d ", arr_1D[k]);
    }

return 0;
}

result:

Enter the number of rows: 4
Enter the number of columns: 3
15  6   60  
91  16  67  
61  72  86  
6   61  91  
15 6 60 91 16 67 61 72 86 6 61 91