剑指offer-从上往下打印二叉树22

class Solution:
    # 返回从上到下每个节点值列表，例：[1,2,3]
    def PrintFromTopToBottom(self, root):
        # write code here
        queen=[]
        res=[]
        if root is not None:
            queen.append(root)
            while len(queen) is not 0:
                temp=queen.pop(0)
                res.append(temp.val)
                if temp.left is not None:
                    queen.append(temp.left)
                if temp.right is not None:
                    queen.append(temp.right)
        return res