fn main() {
    let input = 1234567890;
    let result: Vec<i32> = (0..=(input as f32).log10() as i32)
        .rev()
        .map(|n| input / 10f32.powi(n) as i32 % 10)
        .collect();
    println!("{:?}", result);

    let mut result: Vec<i32> = std::iter::repeat(())
        .scan(input, |state, _| {
            let v = *state;
            *state /= 10;
            match v {0=>None, x => Some(x % 10)}
        })
        .collect();
    result.reverse();
    println!("{:?}", result);

    let mut result = vec![];
    let mut v = input;
    while v != 0 {
        result.push(v % 10);
        v /= 10;
    }
    result.reverse();
    println!("{:?}", result);
}