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
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            int n = Integer.parseInt(in.nextLine());
            String ops = in.nextLine();
            mp3Location(n, ops);
        }
    }

    public static void mp3Location(int n, String ops) {
        int[] songs = new int[n + 1];
        int length = 4;
        int start = 0;
        int end = 3;
        int cur = start;
        if (n < 4) {
            end = n - 1;
            length = n;
        }

        for (int i = 0; i < songs.length; i++) {
            songs[i] = i;
        }
        char[] opsChars = ops.toCharArray();
        for (int i = 0; i < opsChars.length; i++) {
            char opsC = opsChars[i];
            if (opsC == 'U') {
                if (cur == start) {
                    if (start == 0) {
                        //翻页到最后
                        start = n - length;
                        end = n - 1;
                        cur = end;
                    } else {
                        //普通翻页
                        start --;
                        end --;
                        cur = start;
                    }
                } else {
                    cur --;
                }
            }
            if (opsC == 'D') {
                if (cur == end) {
                    if (end == n - 1) {
                        //翻到第一页
                        start = 0;
                        end = length - 1;
                        cur = start;
                    } else {
                        //普通翻页
                        start ++;
                        end ++;
                        cur = end;
                    }
                } else {
                    cur ++;
                }
            }
        }
        for (int i = start; i <= end; i++) {
            System.out.print((songs[i] + 1) + " ");
        }
        System.out.println();
        System.out.println(cur + 1);
    }
}