## 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 < String>(){
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"]