Question

I’m using the following code to sort elements in a std.vector

struct element {
    int order;
    int someValue;
};

int comp( element a, element b ) {
    if (a.order < b.order)
        return true;
    return (rand() % 2) == 0;
}

vector.quickSort(comp);

is this code correct if I’m trying to add randomness on the elements that have the same order value

Answer 1

Is this code correct.

You should really write a test with some data to check that.

---

If you would write a test you would see something wrong and know why, if we look at

if (a.order < b.order)
    return true;
return (rand() % 2) == 0;

you can see that the a.order > b.order case is missing which is why it will incorrectly work for that case, we can fix this by doing this instead which focuses on the exceptional case instead and leaves the other two cases to their default behavior (checking the order):

if (a.order == b.order)
    return (rand() % 2) == 0;
else
    return a.order < b.order;