题解 | #按之字形顺序打印二叉树#

记录

import java.util.ArrayList;
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 {
    public ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
        ArrayList<ArrayList<Integer> > arraylist = new ArrayList<>();
        if (pRoot == null) return arraylist;
        Queue<TreeNode> queue = new LinkedList<TreeNode>();
        queue.add(pRoot);
        int level = 0;
        while (!queue.isEmpty()){
            int len = queue.size();
            ArrayList<Integer> arr = new ArrayList<>();
            for (int i = 0; i < len; i++){
                TreeNode node = queue.poll();
                arr.add(node.val);
                if (node.left != null){
                    queue.add(node.left);
                }
                if (node.right != null){
                    queue.add(node.right);
                }
            }
            if (level % 2 != 0){
                    Collections.reverse(arr);
                }
            level = level + 1;
            arraylist.add(arr);
        }
        return arraylist;















    }

}