LeetCode-面试题32-1-从上到下打印二叉树

[3,9,20,15,7]

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public int[] levelOrder(TreeNode root) {
        if(root==null) return new int[0];
        Queue<TreeNode> queue = new LinkedList<>();
        ArrayList<Integer> alist = new ArrayList<>();
        queue.add(root);
        while(!queue.isEmpty()){
            TreeNode temp = queue.poll();
            alist.add(temp.val);
            if(temp.left!=null)
                queue.add(temp.left);
            if(temp.right!=null)
                queue.add(temp.right);
        }
        return alist.stream().mapToInt(Integer::intValue).toArray();
    }
}

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def levelOrder(self, root: TreeNode) -> List[int]:
        if not root: return []
        quque = [root]
        ans = []
        while quque:
            node = quque.pop(0)
            ans.append(node.val)
            if node.left: quque.append(node.left)
            if node.right: quque.append(node.right)
        return ans