二叉树层序遍历（关键词：树/二叉树/遍历/层序遍历/层次遍历）

二叉树层序遍历

实现

    def levelOrder(self, root):
        if root is None:    return []
        
        res = []
        queue = [root]
        
        while queue != []:
            res.append([node.val for node in queue])
            #res.append([node.val for node in queue if node is not None])
            queue = [kid
                        for node in queue if node is not None
                        for kid in (node.left, node.right) if kid is not None]
        
        return res

参考文献：

1. 这是印象笔记中的笔记，如果是在优快云手机APP上查看此博客，请在印象笔记手机APP中搜索该参考文献：https://app.yinxiang.com/shard/s44/nl/9329661/df25a6f9-1d68-4f9c-bb23-74d202aaa217；
2. https://leetcode.com/problems/binary-tree-level-order-traversal/discuss/33464/5-6-lines-fast-python-solution-(48-ms)?page=1；
3. 102. Binary Tree Level Order Traversal - LeetCode；
4. 15 层次遍历。