60-将⼆叉树打印成多⾏

题⽬描述

从上到下按层打印⼆叉树，同⼀层结点从左⾄右输出。每⼀层输出⼀⾏。

给定的⼆叉树是 {1,2,3,#,#,4,5} :

该⼆叉树多⾏打印层序遍历的结果是：

[
[1],
[2,3],
[4,5]
]

示例1
输⼊：{8,6,10,5,7,9,11}
返回值：[[8],[6,10],[5,7,9,11]]

思路及解答

59题的缩减版，层序遍历

public class Solution {
    ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
        //层次打印遍历树
        ArrayList<ArrayList<Integer> > lists = new ArrayList<>();
        if(pRoot == null) return lists;
        Queue<TreeNode> q = new LinkedList<>();
        q.offer(pRoot);
        while(!q.isEmpty()){
            int size = q.size();
            ArrayList<Integer> list = new ArrayList<>();
            for(int i = 0; i < size; i++){
                TreeNode temp = q.poll();
                list.add(temp.val);
                if(temp.left != null) q.offer(temp.left);
                if(temp.right != null) q.offer(temp.right);
            }
            lists.add(list);
        }
        return lists;
    }
    
}