Generate random numbers without duplicates in a dynamic array C

Question

I want to randomize a dynamic array , with random numbers without duplicates in each column , and each column is limited ,

Check my main.c File

int main()
{
        int i, j;
        int **p;

        srand(time(0));

        p = malloc(9 * sizeof *p);
        for (i=0; i<9; i++) {
                p[i] = malloc (9 * sizeof *p[i]);
        }
        if (errno) {
                perror("startup");
                exit(1);
        }

        for (j=0; j<3; j++) {
                for (i=0; i<9; i++) {
                        p[j][i] = random(j,i);
                }
        }

        for (j=0; j<3; j++) {
                for (i=0; i<9; i++) {
                        printf(" %d ", p[j][i]);
                }
                printf ("\n");
        }
} 

and this is my random function

int random(int *j, int *i)
{
int s = 0;
int b;
int MIN =0;
int MAX=0;
b= i;

switch (b)
{

    case 0:
            MAX = 9;
            MIN = 1;
            s = (rand() % (MAX - MIN + 1)) + MIN;

    break;

case 1:
        MAX = 19;
        MIN = 10;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 2:
        MAX = 29;
        MIN = 20;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 3:
        MAX = 39;
        MIN = 30;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 4:
        MAX = 49;
        MIN = 40;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 5:
        MAX =59;
        MIN = 50;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 6:
        MAX = 69;
        MIN = 60;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 7:
        MAX = 79;
        MIN = 70;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

case 8:
        MAX = 90;
        MIN = 80;
        s = (rand() % (MAX - MIN + 1)) + MIN;
    break;

}
return s;
}

so Now I want to have any other way to do it but I must use dynamic allocation please suggest me anything that can help me out .

Answer 1

I would suggest some changes:

• Allocate the entire matrix with a single allocation, it's easier. It will mean that you must do the indexing manually (i.e. matrix[y * width + x]) but that's usually not too hard.
• It seems you have very tight requirements for the numbers to appear in each column. I would suggest pre-seeding the matrix with all the numbers in sequence, then random shuffling. It's often easier than eliminating dupes.