把二叉树打印成多行

import java.util.*;


/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
        ArrayList<ArrayList<Integer>> result = new ArrayList<>();
        if(pRoot==null){
            return result;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(pRoot);
        int sum = 1;//当前层的元素个数为1；
        while(queue.size()!=0){
            ArrayList<Integer> list = new ArrayList<>();
            while(sum>0){
                TreeNode  t = queue.poll();
                list.add(t.val);
                if(t.left!=null){
                    queue.add(t.left);
                }
                if(t.right!=null){
                    queue.add(t.right);
                }
                sum--;
            }
            sum = queue.size();
            result.add(list);
        }
        return result;
    }

}