题解 | #数字颠倒#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String num = scanner.nextLine();
        System.out.println(solution1(num));
        System.out.println(solution2(num));
        System.out.println(solution3(num));
    }

    public static String solution1(String str) {
        StringBuilder sb = new StringBuilder();
        for (int i = str.toCharArray().length - 1; i >= 0; i--) {
            sb.append(str.charAt(i));
        }
        return sb.toString();
    }

    public static String solution2(String str) {
        int num = Integer.parseInt(str);
        StringBuilder sb = new StringBuilder();
        while (num / 10 > 0) {
            sb.append(num % 10);
            num /= 10;
        }
        return sb.append(num).toString();
    }

    public static String solution3(String str) {
        return new StringBuilder(str).reverse().toString();
    }
}