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);
        Map<Integer, Integer> map = new LinkedHashMap<>();
        while (sc.hasNext()) {
            String a = sc.nextLine();
            for (int i = a.length(); i > 0; i--) {
                String b = a.substring(i - 1, i);
                if (!map.containsKey(Integer.parseInt(b))) {
                    map.put(Integer.parseInt(b), Integer.parseInt(b));
                }
            }
            StringBuilder sb = new StringBuilder();
            map.forEach((key, value) -> sb.append(value));
            System.out.println(sb.toString());
        }
    }
}

哈希表，采用有序的链表结构即可