题解 | #提取不重复的整数#

import java.util.HashSet;
import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        
        while(in.hasNext()){
            HashSet<Character> digitSet = new HashSet<>();
            StringBuilder result = new StringBuilder();
            
            String number = new StringBuilder(in.nextLine()).reverse().toString();
            for(Character ch: number.toCharArray()){
                if(!digitSet.contains(ch)){
                    digitSet.add(ch);
                    result.append(ch);
                }
            }
            
            System.out.println(result);
        }
    }
}