The basic idea is to start from root and add it to the current path, then we recursively visit its left and right subtrees if they exist; otherwise, we have reached a leaf node, so just add the current path to the result paths.

The code is as follows.

1 class Solution { 2 public: 3     vector
     
       binaryTreePaths(TreeNode* root) { 4         vector
      
        paths; 5         string path; 6         treePaths(root, path, paths); 7         return paths; 8     } 9 private:10     void treePaths(TreeNode* node, string path, vector
       
        & paths) {11         if (!node) return;12         path += path.empty() ? to_string(node -> val) : "->" + to_string(node -> val);13         if (!(node -> left) && !(node -> right)) {14             paths.push_back(path);15             return;16         }17         if (node -> left) treePaths(node -> left, path, paths);18         if (node -> right) treePaths(node -> right, path, paths);19     }20 };