Quick sort, Hoare partitioning, using random pivot

Question

Other than below, is there a better way to do quick sort using random pivot(I could not do without a swap)? Please advise

int hoare_par (int *a, int b, int e)
{
    if (b < e) {
        int p_i = __random(b, e);
        __swap(&a[b], &a[p_i])

        int p = a[b];
        b = b - 1;
        e = e + 1;

        while (1) {
            do { ++b;} while (a[b] < p);
            do { --e;} while (a[e] > p);
            if (b < e)
                 __swap( &a[b], &a[e]);
            else
                 return e;
        }
    }
    return e;
}

Also, please let me know if incorrect. Thanks!

Answer 1

If you take a peek at Wikipedia's article and study the pseudocode for Hoare partitioning given there, you'll see that all the partitioning scheme cares about is that the selected pivot is somewhere in the range (it serves as a sentinel to avoid running out of the range for both indices). So you can just pick any element of the range at random as pivot element and do the partitioning as written down there.