树的练习（6）

 很显然，这与前面的一题的本质区别是，不再是简单的追加。要区分追加的分类。

# 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[List[int]]:
        if not root: return []
        res, queue = [], collections.deque()
        queue.append(root)
        while queue:
            tmp = []
            for _ in range(len(queue)):
                node = queue.popleft()
                tmp.append(node.val)
                if node.left: queue.append(node.left)
                if node.right: queue.append(node.right)
            res.append(tmp)
        return res

# 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[List[int]]:
        if not root: return []
        res, queue = [],[root]
        while queue:
            tmp=[]
            for _ in range(len(queue)):
                node = queue.pop(0)
                tmp.append(node.val)
                if node.left: queue.append(node.left)
                if node.right: queue.append(node.right)
            res.append(tmp)
        return res