【剑指offer】22 从上往下打印二叉树
- 题目描述
从上往下打印出二叉树的每个节点，同层节点从左至右打印。
- 解题思路
用arraylist模拟一个队列来存储相应的TreeNode，进行层次遍历。
- Java实现
import java.util.ArrayList;/**public class TreeNode {int val = 0;TreeNode left = null;TreeNode right = null;public TreeNode(int val) {this.val = val;}}*/public class Solution {public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {ArrayList<Integer> list = new ArrayList<>();if (root == null) {return list;}ArrayList<TreeNode> queue = new ArrayList<>();queue.add(root);while (queue.size() != 0) {TreeNode temp = queue.remove(0);if (temp.left != null){queue.add(temp.left);}if (temp.right != null) {queue.add(temp.right);}list.add(temp.val);}return list;}}