fn main() {
    let input = "?? 50 53 31 00 00";
    let parsed = input
        .split(' ')
        .map(|b| {
            if b == "??" {
                Ok(None)
            } else {
                u8::from_str_radix(b, 16).map(Some)
            }
        })
        .collect::<Result<Vec<Option<u8>>, _>>();
    println!("{:?}", parsed);
}