Traffic Light の解説

BYRを配列でもって次ー

fn main() {
    input! {
        c: char
    }
    let byr = "BYR".chars().collect_vec();
    let idx = byr.iter().position(|&e| e == c).unwrap();
    let ans = byr[(idx + 1) % 3];
    println!("{}", ans);
}