剑指offer 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。

解决方案：

import java.util.ArrayList;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
/**
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<Integer>();
ArrayList<TreeNode> queue = new ArrayList<>();
if(root ==null){
return list;
}

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;

}
}