题解 | #数字颠倒#

import java.util.ArrayList;
import java.util.List;
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);
        //Set<Character> ls = new HashSet<>();
        List<Character> ls = new ArrayList<>();
        while (sc.hasNextLine()) {
            String str = sc.nextLine();
            for (int i = str.length()-1; i>=0 ; i--) {
                ls.add(str.charAt(i));
            }
            for (Character i :
                 ls) {
                System.out.print(i);
            }
        }
    }
}