What should I use instead of goto statement?

Question

srand(time(NULL));
for(i=0;i<9;i++)
{
    random: temp=rand()%9;
    for(j=0;j<=i;j++)
    {
        if(temp==randarr[j])
        {
            goto random;
        }
    }
    randarr[i]=temp;
       //   printf("%d ",randarr[i]);
}

I want to generate random numbers between 0 to 8 without repeat any number. I use this code it works perfectly. But I want to remove goto statement from my code. how can i write my code without goto? Thanks!!

Answer 1

You don't want to generate every number randomly. You want to shuffle the numbers from 0 to 8 in some random order.

A far simpler approach (that also eliminates the use of goto) is to start from a sorted array and pick an index to swap with randomly each iteration.

srand(time(NULL));
int randarr[] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
for(int i = 0; i < 9; ++i)
{
    int swap_idx = rand() % 9;
    int temp = randarr[swap_idx];
    randarr[swap_idx] = randarr[i];
    randarr[i] = temp;
}

---

As noted by HolyBlackCat, the naive approach tends to give a non-uniform distribution of the various permutations. If that is a concern for you, an improvement is possible in the form of the Fisher-Yates (or Knuth) shuffle

srand(time(NULL));
int randarr[] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
for(int i = 0; i < 9; ++i)
{
    int swap_idx = i + rand() % (9 - i);
    int temp = randarr[swap_idx];
    randarr[swap_idx] = randarr[i];
    randarr[i] = temp;
}