算法（40）--按之字形顺序打印二叉树

仅记录学习笔记，如有错误欢迎指正。

• 输入:{1,2,3,#,#,4,5}
• 输出: [[1],[3,2],[4,5]]

import java.util.*;


public class Solution {
    public ArrayList> Print(TreeNode pRoot) {
        ArrayList> res = new ArrayList<>();
        if(pRoot == null){
            return res;
        }
      
        linkedList q = new linkedList<>();
        q.push(pRoot);
        int level = 0;
        while(!q.isEmpty()){
            ArrayList list = new ArrayList<>();
            int size = q.size();
            while(size-->0){
                TreeNode cur = q.pop();
                // 层数为奇数末尾添加元素，层数为偶数头部添加元素
                if(level % 2 == 0)
                    list.add(cur.val);
                else
                    list.add(0,cur.val);
                if (cur.left != null)
                    q.addLast(cur.left);
                if (cur.right != null)
                    q.addLast(cur.right);
            }
             res.add(list);
             level++;
        }
        return res;
        
    }

}