打卡群刷题总结0808——二叉树的层序遍历

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def levelOrder(self, root):
        """
        :type root: TreeNode
        :rtype: List[List[int]]
        """
        if not root:
            return []
        res = []
        nodes = [root]
        while len(nodes) > 0:
            tmp = []
            vals = []
            for node in nodes:
                vals.append(node.val)
                if node.left:
                    tmp.append(node.left)
                if node.right:
                    tmp.append(node.right)
            nodes = copy.copy(tmp)
            res.append(vals)
        return res