题解 | #字符逆序#

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 in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            String s = in.nextLine();
            System.out.println(reverseString(s));
        }
    }

    public static String reverseString(String s) {
        int n = s.length();
        char[] charArray = s.toCharArray();
        int left = 0;
        int right = n - 1;
        while (left < right) {
            char ch = charArray[left];
            charArray[left] = charArray[right];
            charArray[right] = ch;
            left++;
            right--;
        }
        return String.valueOf(charArray);
    }
}