Path Sum II @LeetCode

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

	package leetcode.combinations;
	import java.util.ArrayList;
	/**
	* Solution: DFS Traversal + Combination
	* Use sum with traversal to implement to target -- What I think is use another sum += root.val, but obviously,
	* it's more complicated than sum -= root.val;
	*
	* @author jeffwan
	* @date Feb 15, 2014
	*/
	public class PathSum {
	public ArrayList<ArrayList<Integer>> pathSum(TreeNode root, int sum) {
	ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
	ArrayList<Integer> list = new ArrayList<Integer>();
	helper(result, list, root, sum);
	return result;
	}
	private void helper(ArrayList<ArrayList<Integer>> result,
	ArrayList<Integer> list, TreeNode root, int sum) {
	if (root == null) {
	return;
	}
	sum -= root.val;
	if (root.left == null && root.right == null) {
	if (sum == 0) {
	list.add(root.val);
	result.add(new ArrayList<Integer>(list));
	list.remove(list.size() - 1);
	}
	return;
	}
	list.add(root.val);
	helper(result, list, root.left, sum);
	helper(result, list, root.right, sum);
	list.remove(list.size() - 1);
	}
	private class TreeNode {
	int val;
	TreeNode left;
	TreeNode right;
	TreeNode(int x) { this.val = x; }
	}
	}

view raw pathSum.java hosted with ❤ by GitHub