Question

I want to make sure ‘grid’ can’t return 2 same values, but I’m not sure how. Here’s my code:

grid[rnd(2,x-2) * y + rnd(2,y-2)].height = rnd(25,40);

int rnd(int min, int max) {
    return min + rand() % (max - min + 1);
}

I also seeded rand() with srand(time(NULL));

I wish I could provide more details or what I tried, but I couldn’t quite find anything related to this topic.

EDIT: I could of course do re-randoming, but I feel like it’s bad practice :/

Answer 1

If you really need to avoid consecutive repeats,¹ all you need to do is pass the previous value into your function, and then generate random numbers in a loop until it is distinct.

Pseudo-code:

int rnd(..., int prev) {
    int y;
    do {
        y = rand() ...;
    } while (y == prev);
    return y;
}

Note that you could alternatively maintain prev as a static variable inside the function. But this would render it incapable of generating multiple independent streams simultaneously.

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_{1. Which actually makes things less “random”, in the sense of becoming more predictable.}