## Algorithm

Problem Name: 1233. Remove Sub-Folders from the Filesystem

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.

## Code Examples

### #1 Code Example with Java Programming

```Code - Java Programming```

``````
class Solution {
public List removeSubfolders(String[] folder) {
Set set = new HashSet<>();
Arrays.sort(folder, new Comparator(){
public int compare(String s1, String s2) {
return s1.length() - s2.length();
}
});
for (String fl : folder) {
String[] files = fl.split("/");
StringBuilder sb = new StringBuilder();
for (int i = 1; i < files.length; i++) {
sb.append("/").append(files[i]);
if (set.contains(sb.toString())) {
break;
}
}
if (sb.length() > 0) {
}
}
return new ArrayList<>(set);
}
}
``````
Copy The Code &

Input

cmd
folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]

Output

cmd
["/a","/c/d","/c/f"]

### #2 Code Example with Python Programming

```Code - Python Programming```

``````
class Solution:
def removeSubfolders(self, folder: List[str]) -> List[str]:
st = set(folder)
for f in folder:
if any(p in st for p in itertools.accumulate(f.split('/'), lambda x, y: x + '/' + y) if p and p != f):
return list(st)
``````
Copy The Code &

Input

cmd
folder = ["/a","/a/b","/c/d","/c/d/e","/c/f"]

Output

cmd
["/a","/c/d","/c/f"]