Рекурсивное решение задачи №148 от UniLecs (Обработка массива)

main.rs

type Elem = i16;

fn sink_zeros(arr: &mut [Elem]) {
    sink_zeros_recurrent(arr);
}

fn sink_zeros_recurrent(arr: &mut [Elem]) -> usize {
    let rev = arr.iter().rev();
    let non_zeros = rev.clone().take_while(|&&x| x != 0).count();
    let zeros = rev.skip(non_zeros).take_while(|&&x| x == 0).count();
    let len = arr.len();

    if zeros == 0 {
        return len;
    }

    let to_insert = sink_zeros_recurrent(&mut arr[..len - non_zeros - zeros]);
    for (i, j) in (to_insert..).zip(len - non_zeros..len) {
        arr.swap(i, j);
    }

    to_insert + non_zeros
}

fn main() {
    let mut arr = [0, 0, -5, 4, 0, 2, 0];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // [-5, 4, 2, 0, 0, 0, 0]

    let mut arr = [4, 0, 6, 0, 0, -5];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // [4, 6, -5, 0, 0, 0]

    let mut arr = [1, 2, 3, 4, 5, 6];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // [1, 2, 3, 4, 5, 6]

    let mut arr = [0, 0, 0, 0, 0];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // [0, 0, 0, 0, 0]

    let mut arr = [0];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // [0]

    let mut arr = [-2];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // [-2]

    let mut arr = [];
    sink_zeros(&mut arr);
    println!("{:?}", arr); // []
}

Playground: https://play.rust-lang.org/?gist=693c6deb2a7307b02d44d83ca4143a5d
Условия: https://tgraph.io/Anons-148-Obrabotka-massiva-12-19