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.
class Solution:
    def removeSubfolders(self, folder: List[str]) -> List[str]:
        folder.sort()
        
        n = len(folder)
        prev = folder[0]
        
        i = 1
        while i < n:
            curr = folder[i]
            
            if curr.startswith(prev + '/'):
                folder.remove(curr)
                curr = prev
                i-= 1
                n-= 1
                            
            prev = curr
            i+= 1
        
        return folder
class Solution:
    def removeSubfolders(self, folder: List[str]) -> List[str]:
        folder.sort()
        
        n = len(folder)
        prev = folder[0]
        
        i = 1
        while i < n:
            curr = folder[i]
            
            if curr.startswith(prev + '/'):
                folder.remove(curr)
                curr = prev
                i-= 1
                n-= 1
                            
            prev = curr
            i+= 1
        
        return folder