Laskettelukeskus

use std::{io, iter};

#[derive(Clone)]
enum ByteIter<'a> {
    End(std::str::Bytes<'a>),
    Chain(Box<iter::Chain<iter::Take<ByteIter<'a>>, ByteIter<'a>>>),
}

impl Iterator for ByteIter<'_> {
    type Item = u8;

    fn next(&mut self) -> Option<Self::Item> {
        match self {
            Self::End(bytes) => bytes.next(),
            Self::Chain(chain) => chain.next(),
        }
    }
}

fn main() {
    let mut input = String::new();
    io::stdin().read_line(&mut input).unwrap();

    let mut result: Vec<u8> = Vec::with_capacity(input.len());
    let mut bytes = ByteIter::End(input.bytes());
    while let Some(b) = bytes.next() {
        if let Some(n) = (b as char).to_digit(10) {
            bytes = ByteIter::Chain(Box::new(bytes.clone().take(n as usize).chain(bytes)))
        } else {
            result.push(b);
        }
    }
    let output = std::str::from_utf8(&result).unwrap();

    println!("{}", output);
}

Test 1

Group: 1, 2

Verdict: WRONG ANSWER

Test 2

Group: 1, 2

Verdict: WRONG ANSWER

Test 3

Group: 1, 2

Verdict: WRONG ANSWER

Test 4

Group: 2

Verdict: WRONG ANSWER

Test 5

Group: 2

Verdict: WRONG ANSWER

Test 6

Group: 1, 2

Verdict: WRONG ANSWER

Test 7

Group: 2

Verdict: WRONG ANSWER

Test 8

Group: 1, 2

Verdict: WRONG ANSWER

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 1, 2

Verdict: WRONG ANSWER

Test 11

Group: 2

Verdict: WRONG ANSWER

Test 12

Group: 1, 2

Verdict: WRONG ANSWER

Test 13

Group: 2

Verdict: WRONG ANSWER