Path Sum II

1. Title

Path Sum II

2. Http address

https://leetcode.com/problems/path-sum-ii/

3. The question

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]
]

4. My code (AC)

    public static void DFS(TreeNode root,List<Integer> list,int sum)
    {

            if( root == null )
                    return ;
            List<Integer> addlist = null;
            list.add(root.val);
            list.set(0,root.val + list.get(0));
            if( root.left == null && root.right == null )
            {
                if( sum == list.get(0) )
                {
                    addlist = new ArrayList<Integer>(list);
                    addlist.remove(0);
                    re.add(addlist);
                }
            }


            if( root.left != null )
            {
                DFS(root.left,list,sum);
                list.set(0,list.get(0) - root.left.val);
                list.remove(list.size()-1);
            }
            if( root.right != null )
            {
                DFS(root.right,list,sum);
                list.set(0,list.get(0) - root.right.val);
                list.remove(list.size()-1);
            }
            return;
    }
    //Accpeted
    public static List<List<Integer>> pathSum(TreeNode root,int sum){

                re = new ArrayList<List<Integer>>();
                if( root == null )
                        return re;
                List<Integer> list = new ArrayList<Integer>();
                list.add(0);
                DFS(root,list,sum);
                return re;
    }