JZ32 从上往下打印二叉树

JZ32 从上往下打印二叉树

从上往下打印二叉树_牛客题霸_牛客网 (nowcoder.com)

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import java.util.*;
public class Solution {
    public ArrayList<Integer> PrintFromTopToBottom(TreeNode root) {
        ArrayList<Integer> list=new ArrayList<>();
        if(root==null){
            return list;
        }
        Queue<TreeNode> q=new LinkedList<>();
        q.offer(root);
        while(q.isEmpty()==false){
            TreeNode cur=q.poll();
            list.add(cur.val);
            if(cur.left!=null){
                q.offer(cur.left);
            }
            if(cur.right!=null){
                q.offer(cur.right);
            }
        }
        return list;
    }
}