题解 | #字符串反转#

import java.util.*;
import java.io.*;

public class Main{
    public static void main(String [] args) throws Exception{
        BufferedReader bf =  new BufferedReader(new InputStreamReader(System.in));
        char [] arr = bf.readLine().toCharArray();
        StringBuilder sb = new StringBuilder();
        for(int i = arr.length-1; i>=0; i--){
            if(sb.indexOf(String.valueOf(arr[i])) > -1){
                continue;
            }
            sb.append(arr[i]);
        }
        System.out.println(sb.toString());
        
        
    }
}