[Swift]LeetCode1233. 刪除子文件夾 | Remove Sub-Folders from the Filesystem

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Given a list of folders, remove all sub-folders in those folders and return in any order the folders after removing.

If a folder[i] is located within another folder[j], it is called a sub-folder of it.

The format of a path is one or more concatenated strings of the form: / followed by one or more lowercase English letters. For example, /leetcode and /leetcode/problems are valid paths while an empty string and / are not.

Example 1:

Input: folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]
Output: ["/a","/c/d","/c/f"]
Explanation: Folders "/a/b/" is a subfolder of "/a" and "/c/d/e" is inside of folder "/c/d" in our filesystem.
Example 2:

Input: folder = ["/a","/a/b/c","/a/b/d"]
Output: ["/a"]
Explanation: Folders "/a/b/c" and "/a/b/d/" will be removed because they are subfolders of "/a".
Example 3:

Input: folder = ["/a/b/c","/a/b/ca","/a/b/d"]
Output: ["/a/b/c","/a/b/ca","/a/b/d"]

Constraints:

1 <= folder.length <= 4 * 10^4
2 <= folder[i].length <= 100
folder[i] contains only lowercase letters and '/'
folder[i] always starts with character '/'
Each folder name is unique.

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你是一位系統管理員，手裏有一份文件夾列表 folder，你的任務是要刪除該列表中的全部 子文件夾，並以 任意順序 返回剩下的文件夾。

咱們這樣定義「子文件夾」：

若是文件夾 folder[i] 位於另外一個文件夾 folder[j] 下，那麼 folder[i] 就是 folder[j] 的子文件夾。
文件夾的「路徑」是由一個或多個按如下格式串聯造成的字符串：

/ 後跟一個或者多個小寫英文字母。
例如，/leetcode 和 /leetcode/problems 都是有效的路徑，而空字符串和 / 不是。

示例 1：

輸入：folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]
輸出：["/a","/c/d","/c/f"]
解釋："/a/b/" 是 "/a" 的子文件夾，而 "/c/d/e" 是 "/c/d" 的子文件夾。
示例 2：

輸入：folder = ["/a","/a/b/c","/a/b/d"]
輸出：["/a"]
解釋：文件夾 "/a/b/c" 和 "/a/b/d/" 都會被刪除，由於它們都是 "/a" 的子文件夾。
示例 3：

輸入：folder = ["/a/b/c","/a/b/d","/a/b/ca"]
輸出：["/a/b/c","/a/b/ca","/a/b/d"]

提示：

1 <= folder.length <= 4 * 10^42 <= folder[i].length <= 100folder[i] 只包含小寫字母和 /folder[i] 老是以字符 / 起始每一個文件夾名都是惟一的