题解 | #MP3光标位置#

n = int(input())
cmd = input()


def mp4(number, commands):
    c = 1
    l = [1,2,3,4]
    
    for i in cmd:
        if i == 'U':
            c -= 1
            if c not in l and l[0] == 1:
                l = [n-3,n-2,n-1,n]
                c = n
            elif c not in l and l[0] != 1:
                l = [c, c+1, c+2, c+3]
        if i == 'D':
            c +=1
            if c not in l and l[3] == n:
                l = [1,2,3,4]
                c =1
            elif c not in l and l[3] != n:
                l = [c-3, c-2, c-1, c]

    print(*l)
    print(c)


def mp3(number, commands):
    c = 1
    l = []

    for j in range(n):
        l.append(j+1)
    print(*l)  

    for k in cmd:
        if k == 'U':
            c -= 1
        else:
            c += 1
    c = (c + n) % n
    print(c)


if n > 4:
    mp4(n, cmd)
else:
    mp3(n, cmd)

首先按照歌曲数目分类：

1. 数目n <= 4：列表可以直接输出，用%计算最终位置
2. 数目n > 4：判断后输出列表，当前位置随时更新

输出列表情况：

1. 指针在列表内：列表不变
2. 指针移出当前列表，并移到总列表外：重置
3. 指针移出当前列表，但还在总列表内：整体移动当前列表