题解 | #提取不重复的整数#

import java.util.*;
public class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        while (num % 10 == 0) {
            num = sc.nextInt();
        }
        String str = String.valueOf(num);
        char[] chs = str.toCharArray();
        Set<Character> cset = new TreeSet<>();
        List<Character> cl = new ArrayList<>();
        for (int i = chs.length - 1; i >= 0; i--) {
            if (cset.add(chs[i])) { //不重复，true,就是里面还没有
                cl.add(chs[i]);
            }
        }
        for (Character ch : cl) {
            System.out.print(ch);
        }
    }

}