113.path sum ii

 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class  {
    List<List<Integer>> res = new ArrayList<>() ;
    
    
    public List<List<Integer>> pathSum(TreeNode root, int sum) {
        List<Integer> list = new ArrayList<>();
        pathSum2(root, sum, list);
        return res;
        
    }
    
    public void pathSum2(TreeNode root, int sum, List<Integer> resList){
        if(root == null)
            return;
        if(root.left == null && root.right == null && root.val == sum){ // leaf
            resList.add(root.val);
            res.add(resList);
            return;
        }
        resList.add(root.val);
        List<Integer> resnext = new ArrayList(resList);
        pathSum2(root.left, sum-root.val, resnext); 
        resnext = new ArrayList(resList);
        pathSum2(root.right, sum-root.val, resnext);
    }
}