题解 | MP3光标位置

import sys

count = int(input())
s = input()

cursor_pos = 0#记录光标位置
index = 0#记录当前歌曲

for j in s:
    if j == "U":
        # 光标在第一首歌曲的情况
        if cursor_pos == 0:
            if index == 0:
                cursor_pos = 3
        else:
            cursor_pos = cursor_pos - 1
        index = index - 1
        if index < 0:
            index = count - 1

    elif j == "D":
        # 光标在最后一首歌曲的情况
        if cursor_pos == 3:
            if index == count-1:
                cursor_pos = 0
        else:
            cursor_pos = cursor_pos + 1
        index = (index + 1) % count

start = index + 1 - cursor_pos
for i in range(start, start + 3):
    if i >0:
        print(i, end=" ")

print(start + 3)
print(index + 1)