算法:把二叉树打印成多行

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;

public class Solution {
    ArrayList<ArrayList<Integer>> Print(TreeNode pRoot) {
        ArrayList<ArrayList<Integer>> res = new ArrayList<>(128);
        if (pRoot == null) return res;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(pRoot);
        while (!queue.isEmpty()) {
            int size = queue.size();
            ArrayList<Integer> layer = new ArrayList<>();
            for (int i = 0; i < size; ++i) {
                TreeNode temp = queue.poll();
                layer.add(temp.val);
                if (temp.left != null) queue.offer(temp.left);
                if (temp.right != null) queue.offer(temp.right);
            }
            res.add(layer);
        }
        return res;
    }
}