1+ 2+ class Trie :
3+ # current node structure's serialized representation
4+ serial : str = ""
5+ # current node's child nodes
6+ children : dict
7+ 8+ def __init__ (self ):
9+ self .children = dict ()
10+ 11+ 12+ class Solution :
13+ def deleteDuplicateFolder (self , paths : List [List [str ]]) -> List [List [str ]]:
14+ # root node
15+ root = Trie ()
16+ 17+ for path in paths :
18+ cur = root
19+ for node in path :
20+ if node not in cur .children :
21+ cur .children [node ] = Trie ()
22+ cur = cur .children [node ]
23+ 24+ # hash table records the occurrence times of each serialized representation
25+ freq = Counter ()
26+ 27+ # post-order traversal based on depth-first search, calculate the serialized representation of each node structure
28+ def construct (node : Trie ) -> None :
29+ # if it is a leaf node, then the serialization is represented as an empty string, and no operation is required.
30+ if not node .children :
31+ return
32+ 33+ v = list ()
34+ # if it is not a leaf node, the serialization representation of the child node structure needs to be calculated first.
35+ for folder , child in node .children .items ():
36+ construct (child )
37+ v .append (folder + "(" + child .serial + ")" )
38+ 39+ # to prevent issues with order, sorting is needed
40+ v .sort ()
41+ node .serial = "" .join (v )
42+ # add to hash table
43+ freq [node .serial ] += 1
44+ 45+ construct (root )
46+ 47+ ans = list ()
48+ # record the path from the root node to the current node.
49+ path = list ()
50+ 51+ def operate (node : Trie ) -> None :
52+ # if the serialization appears more than once in the hash table, it needs to be deleted.
53+ if freq [node .serial ] > 1 :
54+ return
55+ # otherwise add the path to the answer
56+ if path :
57+ ans .append (path [:])
58+ 59+ for folder , child in node .children .items ():
60+ path .append (folder )
61+ operate (child )
62+ path .pop ()
63+ 64+ operate (root )
65+ return ans
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