Solution.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int sumNumbers(TreeNode root) {
        if (root==null) {
            return 0;
        }
        List<List<TreeNode>> totalList=new ArrayList<List<TreeNode>>();
        List<TreeNode> initList=new ArrayList<TreeNode>();
        initList.add(root);
        totalList.add(initList);
        for (int i = 0; i < totalList.size(); i++) {
            List<TreeNode> list=totalList.get(i);
            TreeNode node=list.get(list.size()-1);
            if (node.left!=null||node.right!=null) {
                if (node.left!=null) {
                    List<TreeNode> newList=new ArrayList<TreeNode>();
                    newList.addAll(list);
                    newList.add(node.left);
                    totalList.add(newList);
                }
                if (node.right!=null) {
                    List<TreeNode> newList=new ArrayList<TreeNode>();
                    newList.addAll(list);
                    newList.add(node.right);
                    totalList.add(newList);
                }
                totalList.remove(i);
                i--;
            }
        }
        long answer=0;
        for (int i = 0; i < totalList.size(); i++) {
            List<TreeNode> list=totalList.get(i);
            long sum=0;
            for (int j = 0; j < list.size(); j++) {
                sum+=list.get(j).val;
                sum*=10;
            }
            sum/=10;
            answer+=sum;
        }
        return Integer.valueOf(""+answer);
    }
}