Generate 8 different Coordination

Question

I'm trying to write a function that gets an array, generates 8 different coordinates. I have some struct Array of size 8 that saves some coordinates in another array([8][8]). I'm trying to get eight different coordinates, but unfortunately, sometimes I get the same coordinates.

Here is the code :

struct location {
int x;
int y;
};
void setCoordinations(struct locaction loc[]) /// the array is empty.
{
    int i = 0, j = 8; 
    srand(time(NULL));


    array[i].x = rand() % 8;
    array[i].y = rand() % 8;
    for (int i = 1; i <8; i++)
    {
        
        array[i].x = (rand() +i) % 8;
        array[i].y= (rand() -j)  % 8;
    }

I understand I can use Fisher–Yates shuffle, but my main problem is that, for example, I can have the coordinates (6,6) once, but I cant have it twice. I need 8 random unique coordinates.

How would I implement this?

Answer 1

If algorithm (unique coordinates) here is a problem check your newly create coordinates with already created coordinates in array.

void setCoordinations(struct locaction loc[]) /// the array is empty.
{
    int i, j = 8, k; 
    srand(time(NULL));

    loc[0].x = rand() % 8;
    loc[0].y = rand() % 8;
    for (i = 1; i < 8; )
    {
        loc[i].x = (rand() + i) % 8;
        loc[i].y = (rand() - j) % 8;
        for (k = 0; k < i; k++)         // check in already created coordinates
            if(loc[i].x == loc[k].x && loc[i].y == loc[k].y)
                break;
        if(k == i)                      // no match found
            i++;                        // create next coordinates[i]
                                        //   otherwise create coordinates again
    }