题解 | #MP3光标位置#

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String[] args) {
        BufferedReader r = new BufferedReader(new InputStreamReader(System.in));
        String a, b;
        try {
            a = r.readLine();
            b = r.readLine();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        char[] chs = a.toCharArray();//歌曲数量1<=n<=150
        char[] operate = b.toCharArray();//命令长度1<=s<=100
        int i = 0, l1 = chs.length, l2 = operate.length, n = 0, current = 0, j = 0,
            capacity = 4;
        while (i < l1) {//得到歌曲的总数量
            if (chs[i] == ' ') break;
            n *= 10;
            n += chs[i] - '0';
            i++;
        }
        int[] songs = new int[n];
        i = 0;
        while (i < n) {//初始化歌曲数组，数组值表示歌曲的编号
            songs[i] = i + 1;
            i++;
        }
        a = "";
        if (n < capacity + 1) {//歌曲数量小于4
            for (i = 0; i < n; i++) {
                a = a + songs[i] + " ";
            }
            i = 0;
            while (i < l2) {//经过操作后，获得当前选中的歌曲索引
                current += (operate[i] == 'U' ? -1 :
                            1);//将向上走转换为索引-1，向下走转换为索引+1
                if (current < 0) current += n;//当选中索引为-1时，跳到最后一个
                else if (current > n - 1) current -=
                        n;//当选中索引为n时，跳到第一个，0~n-1为数组的有效索引
                i++;
            }
        } else {
            for (i = 0; i < l2; i++) {
                current += (operate[i] == 'U' ? -1 : 1);
                if (current <
                        0) {//当选中索引为-1时，页面跳到索引为n-4，n-3,n-2,n-1，因为j为页面首索引，所以j为n-4
                    j = n - 4;
                    current += n;
                }
                if (current > n -
                        1) {//当选中索引为n时，页面跳到索引为0,1,2,4，因为j为页面首索引，所以j为0
                    current -= n;
                    j = 0;
                }
                if (current > j + 3) j = current -
                                             3;//当选中索引比当前页面尾索引大时，首索引j为当前选中索引-3
                if (current < j) j =
                        current;//当选中索引比当前页面首索引小时，首索引j为当前选中索引
            }
            i = j;
            while (i < j + 4) {
                a = a + songs[i] + " ";
                i++;
            }
        }
        a = a + "\n" + songs[current];
        System.out.print(a);
    }
}