Create remove-sub-folders-from-the-filesystem.cpp

Author: kamyu104

C++/remove-sub-folders-from-the-filesystem.cpp

@@ -0,0 +1,76 @@
+// Time:  O(n), n is the total sum of the lengths of folder names
+// Space: O(t), t is the number of nodes in trie
+
+class Solution {
+public:
+    vector<string> removeSubfolders(vector<string>& folder) {
+        TrieNode trie;
+        for (const auto& s : folder) {
+            trie.Insert(split(s, '/'));
+        }
+        vector<string> result;
+        vector<string> path;
+        dfs(&trie, &path, &result);
+        return result;
+    }
+
+private:
+    struct TrieNode {
+        bool is_end = false;
+        unordered_map<string, TrieNode *> leaves;
+
+        void Insert(const vector<string>& s) {
+            auto* p = this;
+            for (const auto& c : s) {
+                if (c.empty()) {
+                    continue;
+                }
+                if (!p->leaves.count(c)) {
+                    p->leaves[c] = new TrieNode;
+                }
+                p = p->leaves[c];
+            }
+            p->is_end = true;
+        }
+
+        ~TrieNode() {
+            for (auto& kv : leaves) {
+                if (kv.second) {
+                    delete kv.second;
+                }
+            }
+        }
+    };
+    
+    void dfs(TrieNode *curr, vector<string> *path, vector<string> *result) {
+        if (curr->is_end) {
+            result->emplace_back(join(*path, '/'));
+            return;
+        }
+        for (const auto& kvp : curr->leaves) {
+            path->emplace_back(kvp.first);
+            dfs(kvp.second, path, result);
+            path->pop_back();
+        }
+    }
+
+    vector<string> split(const string& s, const char delim) {
+        vector<string> result;
+        auto end = string::npos;
+        do {
+            const auto& start = end + 1;
+            end = s.find(delim, start);
+            result.emplace_back(s.substr(start, end - start));
+        } while (end != string::npos); 
+        return result;
+    }
+
+    string join(const vector<string>& names, const char delim) {
+        string result;
+        for (const auto& name : names) {
+            result.push_back('/');
+            result += name;
+        }
+        return result;
+    }
+};