题解 | #提取不重复的整数#

import java.util.HashMap;
import java.util.Map;
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 sc = new Scanner(System.in);
        Map<Character, Integer> map ;
        while (sc.hasNextLine()) {
            String num = sc.nextLine();
            map = new HashMap<>(num.length());
            for (int i = num.length() - 1; i >= 0; i--) {
                Integer integer = map.putIfAbsent(num.charAt(i), 1);
                if (integer == null) {
                    System.out.print(num.charAt(i));
                }
            }
            System.out.println();
        }

    }
}