按层遍历二叉树(不分层) -- 漫漫算法路 刷题篇

import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
/**
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<TreeNode> de = new ArrayList<>();
TreeNode te = root;
de.add(root);
ArrayList<Integer> list = new ArrayList<Integer>();
if(root==null){
return list;
}
while(de.size()!=0){
TreeNode tem = de.remove(0);
if(tem.left!=null){
de.add(tem.left);
}
if(tem.right!=null){
de.add(tem.right);
}
list.add(tem.val);
}
return list;
}
}