diff --git a/LeetCode/606. Construct String from Binary Tree b/LeetCode/606. Construct String from Binary Tree
new file mode 100644
index 0000000..a2d8460
--- /dev/null
+++ b/LeetCode/606. Construct String from Binary Tree	
@@ -0,0 +1,26 @@
+class Solution {
+public:
+    string str = "";
+    
+    void dfs(TreeNode* node, TreeNode* root) {
+        if (node == NULL)
+            return;
+        
+        if (node != root)
+            str += '(';
+        str += to_string(node->val);
+        dfs(node->left, root);
+        if (node->left==NULL && node->right!=NULL)
+            str += "()";
+        
+        dfs(node->right, root);
+        if (node != root)
+            str += ')';
+    }
+    
+    string tree2str(TreeNode* root) {
+        dfs(root, root);
+        
+        return str;
+    }
+};
diff --git a/LeetCode/609. Find Duplicate File in System b/LeetCode/609. Find Duplicate File in System
new file mode 100644
index 0000000..3979d5a
--- /dev/null
+++ b/LeetCode/609. Find Duplicate File in System	
@@ -0,0 +1,40 @@
+class Solution {
+public:
+    vector<vector<string>> findDuplicate(vector<string>& paths) {
+        vector<vector<string>> ans;
+        unordered_map<string, vector<string>> m;
+
+        for (auto i: paths) {
+            string chunk = "", path = "";
+            stringstream ss(i);
+
+            while(ss >> chunk) {
+                // cout<<chunk<<endl;
+                
+                if (path == "") {  // this will run, if the chunk is a path
+                    path = chunk;
+                    continue;
+                }
+
+                // this will run, if the chunk is a file    
+                string reversedContent = "";
+                for (int j=chunk.length()-1; chunk[--j] != '(';)
+                    reversedContent += chunk[j];
+                // cout<<"reversed content = "<<reversedContent<<endl;
+
+                string fileName = "";
+                for (int j=0; chunk[j] != '('; j++)
+                    fileName += chunk[j];
+                // cout<<"fileName = "<<fileName<<endl;
+
+                m[reversedContent].push_back(path + '/' + fileName);
+            }
+        }
+
+        for (auto &[revContent, pathAndFile]: m)
+            if (pathAndFile.size() > 1)
+                ans.push_back(pathAndFile);
+
+        return ans;
+    }
+};