#![allow(non_upper_case_globals)]
#![allow(unused_imports)]
#![allow(dead_code)]
use crate::prelude::*;

pub type I = &'static str;
pub type O = String;

fn checksum (data: &str) -> String {
    data.chars().array_chunks().map(|[a, b]| if a == b { '1' } else { '0' }).collect()
}

fn _solve (data: I, disk: usize) -> O {
    let mut s = data.to_owned();
    while s.len() < disk {
        s = format!("{}0{}", &s, s.chars().rev().map(|e| if e == '1' { '0' } else { '1' }).collect::<String>());
    }
    s = (&s[..disk]).to_owned();
    let mut chk = checksum(&s);
    while chk.len() % 2 == 0 {
        chk = checksum(&chk);
    }
    chk
}

#[cfg(test)]
mod test {
    use super::*;

    const input: &'static str = "01110110101001000";

    #[test]
    fn silver () {
        let ans = _solve(input, 272);
        assert_eq!(ans, s!("11100111011101111"))
    }

    #[test]
    fn gold () {
        let ans = _solve(input, 35651584);

        assert_eq!(ans, s!("10001110010000110"))
    }
}