题解 | #提取不重复的整数#

import java.util.*;
public class Main{
public static void main(){
Scanner scanner = new Scanner(System.in);
String str = scanner.nextLine();
char[] arr = str.toCharArray();
Set set = new HashSet();
StringBuffer sb = new StringBuffer();

    for(int i = arr.length-1; i >=0 ; i--){
        if(set.add(arr[i])){
            sb.append(arr[i]);
        }
    }
    System.out.println(sb);
}

}