vector<vector<int> > pathSum(TreeNode *root, int sum) {

vector<vector<int> > result;

vector<int> v;

generatePathSum(root, sum, 0, v, result);

return result;

}

void generatePathSum(TreeNode *root, int sum, int s, vector<int> v, vector<vector<int> >& result) {

if (root==NULL) return ;

s += root->val;

v.push_back(root->val);

if ( root->left==NULL && root->right==NULL) {

if (s == sum) result.push_back(v);

return;

}

generatePathSum(root->left, sum, s, v, result);

generatePathSum(root->right, sum, s, v, result);

}