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# 1233. Remove Sub-Folders from the Filesystem

<https://leetcode.com/problems/remove-sub-folders-from-the-filesystem>

## Description

Given a list of folders `folder`, return *the folders after removing all **sub-folders** in those folders*. You may return the answer in **any order**.

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 * 104`
* `2 <= folder[i].length <= 100`
* `folder[i]` contains only lowercase letters and `'/'`.
* `folder[i]` always starts with the character `'/'`.
* Each folder name is **unique**.

## ac

```java
```