题解 | #HJ9 提取不重复数字#

用hashset判断数字是否出现过，未出现则输出

public class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt(),num=0;
        HashSet<Integer> st=new HashSet<>();
        while(n%10!=0){
            num=n%10;
            n=n/10;
            if(st.contains(num))continue;
            st.add(num);
            System.out.print(num);
            
        }
    }
}