题解 | #提取不重复的整数#

import java.util.Scanner;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
//        String line1 = in.nextLine();
        String line = in.nextLine();
        char[] chars = line.toCharArray();
        HashMap<Character, Character> map = new HashMap<>();
        //set 不重复集合
        HashSet<Character> set = new HashSet<>();
        ArrayList<Character> list = new ArrayList<>();
        for (int i = chars.length - 1; i >= 0;  i--) {

            if (!(set.contains(chars[i]))) {
                set.add(chars[i]);
                list.add(chars[i]);
            }

        }
        //正向遍历list
        for (int i = 0; i < list.size(); i++) {
            System.out.print(list.get(i));
        }




    }

}