1 vector<int> path; 2      3 int sumNumbers(TreeNode *root) { 4         if (!root) 5             return 0; 6              7         int sum = 0; 8         path.push_back(root->val); 9         10         if (!root->left && !root->right) {11             for (int i = 0; i < path.size(); i++)12                 sum = sum * 10 + path[i];13         }14         else {15             if (root->left)16                 sum += sumNumbers(root->left);17             if (root->right)18                 sum += sumNumbers(root->right);19         }20         21         path.pop_back();22         23         return sum;24 }