/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<List<Integer>> pathSum(TreeNode root, int sum) {
List<Integer> path = new ArrayList<Integer>();
List<List<Integer>> rst = new ArrayList(path);
helper(root, sum, 0, path, rst);
return rst;
}
private void helper(TreeNode root, int sum, int count, List<Integer> path, List<List<Integer>> rst) {
if (root == null) return;
path.add(root.val);
count += root.val;
if (root.left == null && root.right == null && count == sum) {
rst.add(new ArrayList(path));
}
helper(root.left, sum, count, path, rst);
helper(root.right, sum, count, path, rst);
path.remove(path.size() - 1);
}
}