My QQ number Rust quiz

dec_qq_number.rs

// https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=3a2c2557cb1b7d0a313c1e011ba16844

use rand::prelude::*;

fn main() {
    let mut rng = SmallRng::from_seed([0x56u8; 32]);
    (0..10).for_each(|_| (rng.next_u32(), ()).1);
    let key: [u8; 20] = [
        70, 121, 148, 150, 158, 158, 73, 14, 197, 164, 232, 30, 239, 6, 112, 10, 130, 30, 55, 173,
    ];
    let mut bytes = [0; 20];
    rng.fill_bytes(&bytes);
    for b in 0..20 {
        bytes[b] = key[b].wrapping_sub(bytes[b]);
    }
    assert_eq!(&bytes[15..], &[0; 5], "Invalid key");
    let nums = &bytes[1..(bytes[0] as usize)];
    println!(
        "{}",
        nums.iter()
            .map(|n| n.to_string())
            .collect::<Vec<_>>()
            .join("")
    );
}