1948. Delete Duplicate Folders in System LeetCode Solution
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Problem Statement of Delete Duplicate Folders in System
Due to a bug, there are many duplicate folders in a file system. You are given a 2D array paths, where paths[i] is an array representing an absolute path to the ith folder in the file system.
For example, [“one”, “two”, “three”] represents the path “/one/two/three”.
Two folders (not necessarily on the same level) are identical if they contain the same non-empty set of identical subfolders and underlying subfolder structure. The folders do not need to be at the root level to be identical. If two or more folders are identical, then mark the folders as well as all their subfolders.
For example, folders “/a” and “/b” in the file structure below are identical. They (as well as their subfolders) should all be marked:
/a
/a/x
/a/x/y
/a/z
/b
/b/x
/b/x/y
/b/z
However, if the file structure also included the path “/b/w”, then the folders “/a” and “/b” would not be identical. Note that “/a/x” and “/b/x” would still be considered identical even with the added folder.
Once all the identical folders and their subfolders have been marked, the file system will delete all of them. The file system only runs the deletion once, so any folders that become identical after the initial deletion are not deleted.
Return the 2D array ans containing the paths of the remaining folders after deleting all the marked folders. The paths may be returned in any order.
Example 1:
Input: paths = [[“a”],[“c”],[“d”],[“a”,”b”],[“c”,”b”],[“d”,”a”]]
Output: [[“d”],[“d”,”a”]]
Explanation: The file structure is as shown.
Folders “/a” and “/c” (and their subfolders) are marked for deletion because they both contain an empty
folder named “b”.
Example 2:
Input: paths = [[“a”],[“c”],[“a”,”b”],[“c”,”b”],[“a”,”b”,”x”],[“a”,”b”,”x”,”y”],[“w”],[“w”,”y”]]
Output: [[“c”],[“c”,”b”],[“a”],[“a”,”b”]]
Explanation: The file structure is as shown.
Folders “/a/b/x” and “/w” (and their subfolders) are marked for deletion because they both contain an empty folder named “y”.
Note that folders “/a” and “/c” are identical after the deletion, but they are not deleted because they were not marked beforehand.
Example 3:
Input: paths = [[“a”,”b”],[“c”,”d”],[“c”],[“a”]]
Output: [[“c”],[“c”,”d”],[“a”],[“a”,”b”]]
Explanation: All folders are unique in the file system.
Note that the returned array can be in a different order as the order does not matter.
Constraints:
1 <= paths.length <= 2 * 104
1 <= paths[i].length <= 500
1 <= paths[i][j].length <= 10
1 <= sum(paths[i][j].length) <= 2 * 105
path[i][j] consists of lowercase English letters.
No two paths lead to the same folder.
For any folder not at the root level, its parent folder will also be in the input.
Complexity Analysis
Time Complexity: O(10 \cdot \Sigma |\texttt{paths[i][j]}|)
Space Complexity: O(10 \cdot \Sigma |\texttt{paths[i][j]}|)
1948. Delete Duplicate Folders in System LeetCode Solution in C++
1948. Delete Duplicate Folders in System LeetCode Solution in Java
class TrieNode {
public Map<String, TrieNode> children = new HashMap<>();
public boolean deleted = false;
}
class Solution {
public List<List<String>> deleteDuplicateFolder(List<List<String>> paths) {
List<List<String>> ans = new ArrayList<>();
Map<String, List<TrieNode>> subtreeToNodes = new HashMap<>();
Collections.sort(paths, (a, b) -> {
for (int i = 0; i < Math.min(a.size(), b.size()); ++i) {
final int c = a.get(i).compareTo(b.get(i));
if (c != 0)
return c;
}
return Integer.compare(a.size(), b.size());
});
for (List<String> path : paths) {
TrieNode node = root;
for (final String s : path) {
node.children.putIfAbsent(s, new TrieNode());
node = node.children.get(s);
}
}
buildSubtreeToRoots(root, subtreeToNodes);
for (List<TrieNode> nodes : subtreeToNodes.values())
if (nodes.size() > 1)
for (TrieNode node : nodes)
node.deleted = true;
constructPath(root, new ArrayList<>(), ans);
return ans;
}
private TrieNode root = new TrieNode();
private StringBuilder buildSubtreeToRoots(TrieNode node,
Map<String, List<TrieNode>> subtreeToNodes) {
StringBuilder sb = new StringBuilder("(");
for (final String s : node.children.keySet()) {
TrieNode child = node.children.get(s);
sb.append(s).append(buildSubtreeToRoots(child, subtreeToNodes));
}
sb.append(")");
final String subtree = sb.toString();
if (!subtree.equals("()")) {
subtreeToNodes.putIfAbsent(subtree, new ArrayList<>());
subtreeToNodes.get(subtree).add(node);
}
return sb;
}
private void constructPath(TrieNode node, List<String> path, List<List<String>> ans) {
for (final String s : node.children.keySet()) {
TrieNode child = node.children.get(s);
if (!child.deleted) {
path.add(s);
constructPath(child, path, ans);
path.remove(path.size() - 1);
}
}
if (!path.isEmpty())
ans.add(new ArrayList<>(path));
}
} // code provided by PROGIEZ
1948. Delete Duplicate Folders in System LeetCode Solution in Python
class TrieNode:
def __init__(self):
self.children: dict[str, TrieNode] = collections.defaultdict(TrieNode)
self.deleted = False
class Solution:
def deleteDuplicateFolder(self, paths: list[list[str]]) -> list[list[str]]:
ans = []
root = TrieNode()
subtreeToNodes: dict[str, list[TrieNode]] = collections.defaultdict(list)
# Construct the Trie
for path in sorted(paths):
node = root
for s in path:
node = node.children[s]
# For each subtree, fill in the {subtree encoding: [root]} hash table
def buildSubtreeToRoots(node: TrieNode) -> str:
subtree = '(' + ''.join(s + buildSubtreeToRoots(node.children[s])
for s in node.children) + ')'
if subtree != '()':
subtreeToNodes[subtree].append(node)
return subtree
buildSubtreeToRoots(root)
# Mark nodes that should be deleted
for nodes in subtreeToNodes.values():
if len(nodes) > 1:
for node in nodes:
node.deleted = True
# Construct the answer array for nodes that haven't been deleted
def constructPath(node: TrieNode, path: list[str]) -> None:
for s, child in node.children.items():
if not child.deleted:
constructPath(child, path + [s])
if path:
ans.append(path)
constructPath(root, [])
return ans # code by PROGIEZ
