#[allow(unused_macros)] macro_rules! debug { ($($a:expr),* $(,)*) => { #[cfg(debug_assertions)] eprintln!(concat!($("| ", stringify!($a), "={:?} "),*, "|"), $(&$a),*); }; } #[derive(Debug)] struct Input { n: usize, a: Vec, } fn main() { let Input { n, a } = Input::read(std::io::stdin().lock()); let mut v: Vec<_> = a.into_iter().enumerate().collect(); v.sort_by(|(_, x), (_, y)| x.cmp(y)); let mut v: Vec<_> = v.into_iter().map(|(i, _)| i + 1).collect(); v.reverse(); // ひっくり返したものも正答 println!( "{}", v.iter() .chain(v.iter().rev()) .chain(v.iter()) .skip_while(|&&x| x != 1) .step_by(2) .take(n + 1) .map(ToString::to_string) .collect::>() .join(" ") ); } /* 入力の厳密な受け取り * フォーマットのチェック * 制約のチェック */ impl Input { fn read(mut input: T) -> Input { let n = { let mut buffer = String::new(); input.read_line(&mut buffer).unwrap(); match &split(&buffer).unwrap()[..] { &[n] => n.parse().unwrap(), _ => panic!("input format error: N"), } }; let a: Vec = { let mut buffer = String::new(); input.read_line(&mut buffer).unwrap(); split(&buffer) .unwrap() .into_iter() .map(|x| x.parse().unwrap()) .collect() }; assert!(matches!(n, 2..=200_000)); assert_eq!(n, a.len()); assert!(a.iter().all(|x| matches!(x, 1..=1_000_000_000))); { let mut tmp = a.clone(); tmp.sort(); assert!(tmp.windows(2).all(|x| x[0] != x[1])); } Input { n: n, a: a } } } fn split(s: &str) -> Option> { enum State { Word(usize), Space, End, } let mut state = State::Word(0); let mut ret = Vec::new(); for (i, c) in s.char_indices() { let prev = match state { State::End => return None, State::Word(i) => i, State::Space => { state = State::Word(i); i } }; if c == ' ' || c == '\n' { ret.push(&s[prev..i]); state = if c == ' ' { State::Space } else { State::End }; } } matches!(state, State::End).then(|| ret) } #[test] fn test_split() { assert_eq!(split("word\n"), Some(vec!["word"])); assert_eq!( split("many words separated\n"), Some(vec!["many", "words", "separated"]) ); assert_eq!( split(" extra spaces \n"), Some(vec!["", "extra", "", "spaces", ""]) ); assert_eq!(split("no line feed"), None); assert_eq!(split("extra characters\nafter line feed"), None); }