Leetcode Problem 1233 Remove Sub-Folders from the Filesystem.txt

1233. Remove Sub-Folders from the Filesystem
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.


Hint to solve: Use trie and perform DFS until we find a end marked on that path.

class Node:
    def __init__(self):
        self.children = {}
        self.isEnd = False

class Trie:
    def __init__(self):
        self.root = Node()
    
    def insert(self, fullFolderPath):
        folderHierarchyPointer = self.root
        
        folders = fullFolderPath.split('/')
        for folder in folders:
            if folder == '':
                continue
                
            if folder not in folderHierarchyPointer.children:
                folderHierarchyPointer.children[folder] = Node()
            folderHierarchyPointer = folderHierarchyPointer.children[folder]
        folderHierarchyPointer.isEnd = True
    
    
    def findAllTopLevelFolders(self):
        
        def dfs(currentPath, currentFolderPointer):
            if currentFolderPointer.isEnd:
                uniqueFolders.append(currentPath)
                return
            
            for subfolder in currentFolderPointer.children:
                dfs(currentPath+ '/'+ subfolder, currentFolderPointer.children[subfolder])
        uniqueFolders = []
        dfs("", self.root)
        return uniqueFolders

class Solution:
    def removeSubfolders(self, folder: List[str]) -> List[str]:
        
        folderTrie = Trie()
        for folderPath in folder:
            folderTrie.insert(folderPath)
        
        return folderTrie.findAllTopLevelFolders()