题解 | #提取不重复的整数#

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        HashSet<Integer> hs = new HashSet<>();
        String str = sc.next();
        for (int i = str.length() - 1; i >= 0; i--) {
            int n = Integer.parseInt(String.valueOf(str.charAt(i)));
            if(hs.add(n)){
                System.out.print(n);
            }
        }
    }
}