待解决)leetcode 路径和 dfs 线序遍历

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]
]

1。下面的搜索总超时，可能我写的不好

 /**
  * Definition for binary tree
  * public class TreeNode {
  *     int val;
  *     TreeNode left;
  *     TreeNode right;
  *     TreeNode(int x) { val = x; }
  * }
  */
 public class Solution {
     ArrayList<ArrayList<Integer>> list=new ArrayList<ArrayList<Integer>>();
      ArrayList<Integer> arry=new ArrayList<Integer>();

     public List<List<Integer>> pathSum(TreeNode root, int sum) {

         if(root==null) return (List)list;
         if(root.right==null&&root.left==null)
         {
             if(sum==root.val)
             {

             list.add(new ArrayList(arry));
             }
         }

            arry.add(root.val);
         pathSum(root.right,sum-root.val);

         pathSum(root.left,sum-root.val);

         return (List)list;

     }

 }

iew Co