Well, a typical backtracking problem. The code is as follows. You may walk through it using the example in the problem statement to see how it works.

1 class Solution { 2 public: 3     vector
     
      
       > pathSum(TreeNode* root, int sum) { 4         vector
       
        
          > paths; 5         vector
         
           path; 6         findPaths(root, sum, path, paths); 7         return paths;   8     } 9 private:10     void findPaths(TreeNode* node, int sum, vector
          
           & path, vector
           
            
              >& paths) {11 if (!node) return;12 path.push_back(node -> val);13 if (!(node -> left) && !(node -> right) && sum == node -> val)14 paths.push_back(path);15 findPaths(node -> left, sum - node -> val, path, paths);16 findPaths(node -> right, sum - node -> val, path, paths);17 path.pop_back();18 }19 };