feat: Add Solution.java

solution/1900-1999/1948.Delete Duplicate Folders in System/Solution.java

@@ -0,0 +1,117 @@
+import java.util.*;
+
+class TrieNode {
+    Map<String, TrieNode> children;
+    Integer id;
+
+    public TrieNode() {
+        this.children = new HashMap<>();
+        this.id = null;
+    }
+}
+
+public class Solution {
+    public List<List<String>> deleteDuplicateFolder(List<List<String>> paths) {
+        TrieNode root = new TrieNode();
+
+        // Step 1: Build Trie (Tree)
+        for (List<String> path : paths) {
+            TrieNode node = root;
+            for (String folder : path) {
+                node = node.children.computeIfAbsent(folder, k -> new TrieNode());
+            }
+        }
+
+        // Step 2: Assign unique IDs to subtrees
+        Map<String, List<TrieNode>> subtreeMap = new HashMap<>();
+
+        getSubtreeId(root, subtreeMap);
+
+        // Step 3: Mark duplicates
+        Set<TrieNode> duplicates = new HashSet<>();
+        for (List<TrieNode> nodes : subtreeMap.values()) {
+            if (nodes.size() > 1) { // If more than one node has the same structure, mark as duplicate
+                duplicates.addAll(nodes);
+            }
+        }
+
+        // Step 4: Collect remaining paths
+        List<List<String>> ans = new ArrayList<>();
+        collectRemainingPaths(root, new ArrayList<>(), duplicates, ans);
+
+        return ans;
+    }
+
+    private String getSubtreeId(TrieNode node, Map<String, List<TrieNode>> subtreeMap) {
+        if (node.children.isEmpty()) {
+            return ""; // Empty subtree has no ID
+        }
+
+        // Sort children lexicographically and form a string representing the subtree
+        List<String> subtreeList = new ArrayList<>();
+        for (Map.Entry<String, TrieNode> entry : node.children.entrySet()) {
+            String folder = entry.getKey();
+            TrieNode child = entry.getValue();
+            subtreeList.add(folder + "(" + getSubtreeId(child, subtreeMap) + ")");
+        }
+        Collections.sort(subtreeList);
+
+        // Create a unique string representation of the subtree
+        String subtree = String.join(",", subtreeList);
+
+        // Map the subtree representation to the node
+        subtreeMap.computeIfAbsent(subtree, k -> new ArrayList<>()).add(node);
+
+        return subtree;
+    }
+
+    private void collectRemainingPaths(TrieNode node, List<String> path, Set<TrieNode> duplicates, List<List<String>> ans) {
+        if (duplicates.contains(node)) {
+            return; // Skip this subtree because it is marked for deletion
+        }
+
+        if (!path.isEmpty()) {
+            ans.add(new ArrayList<>(path));
+        }
+
+        for (Map.Entry<String, TrieNode> entry : node.children.entrySet()) {
+            path.add(entry.getKey());
+            collectRemainingPaths(entry.getValue(), path, duplicates, ans);
+            path.remove(path.size() - 1);
+        }
+    }
+
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+
+        List<List<String>> paths1 = Arrays.asList(
+                Arrays.asList("a"),
+                Arrays.asList("c"),
+                Arrays.asList("d"),
+                Arrays.asList("a", "b"),
+                Arrays.asList("c", "b"),
+                Arrays.asList("d", "a")
+        );
+
+        List<List<String>> result1 = sol.deleteDuplicateFolder(paths1);
+        for (List<String> path : result1) {
+            System.out.println(path);
+        }
+
+        List<List<String>> paths2 = Arrays.asList(
+                Arrays.asList("a"),
+                Arrays.asList("c"),
+                Arrays.asList("a", "b"),
+                Arrays.asList("c", "b"),
+                Arrays.asList("a", "b", "x"),
+                Arrays.asList("a", "b", "x", "y"),
+                Arrays.asList("w"),
+                Arrays.asList("w", "y")
+        );
+
+        List<List<String>> result2 = sol.deleteDuplicateFolder(paths2);
+        for (List<String> path : result2) {
+            System.out.println(path);
+        }
+    }
+}