quicksort implementation using rust

quicksort.rs

fn main() {
    let mut v = vec![4, 6, 7, 8, 5, 1, 2, 3, 15, 10, 35, 8, 2, 1, 201, 100];
    println!("before: {:?}", v);
    sort_in_place(&mut v);
    println!("after:  {:?}", v);
}

fn sort_in_place(a: &mut [u32]) {
    match a.len() {
        0 | 1 => (),
        2 => if a[1] < a[0] { a.swap(0, 1) },
        _ => {
            let pi = partition(a);
            println!("a {:?}", a);
            sort_in_place(&mut a[..pi]);
            sort_in_place(&mut a[pi + 1..]);
        }
    }
}

fn partition(a: &mut [u32]) -> usize {
    let len = a.len();
    let pi = a.len() - 1;
    a.swap(len / 2, pi); // Take pivot element from the middle and move to the end.
    let mut i = 0;
    let mut j = 0;
    while j < pi {
        if a[j] < a[pi] {
            a.swap(i, j);
            i += 1;
        }
        j += 1;
    }
    a.swap(i, pi);
    i
}