题解 | MP3光标位置

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
        int num = in.nextInt();
        int size;
        if (num < 4) {
            size = num;
        } else {
            size = 4;
        }
        int nowlist = 1;
        int nowpage = 1;
        in.nextLine();
        char[] gnis = in.nextLine().toCharArray();
        for (char ac : gnis) {
            if (ac == 'U') {
                if (nowpage > nowlist) {
                    nowpage--;
                } else if (nowpage == nowlist && nowlist != 1) {
                    nowlist--;
                    nowpage--;
                } else {
                    nowlist = num - (size - 1);
                    nowpage = num;
                }
            } else {
                if (nowpage < nowlist + (size - 1)) {
                    nowpage++;
                } else if (nowpage == nowlist + (size - 1) && nowlist != num - (size - 1)) {
                    nowlist++;
                    nowpage++;
                } else {
                    nowlist = 1;
                    nowpage = 1;
                }
            }
        }
        for (int i = 0; i < size ; i++) {
            System.out.print(nowlist + i + " ");
        }
        System.out.println();
        System.out.print(nowpage);
    }
}