题解 | #求二叉树的层序遍历#Python 无引用queue包

class Solution:
    def levelOrder(self , root ):
        # write code here
        p = root
        if not p:
            return None
        list = []
        list1 = []
        list1.append(p)
        while list1:
            list2 = []   #存放指针
            list3 = []   #存放val值
            for i in range(len(list1)):
                list3.append(list1[i].val)
                if list1[i].left:
                    list2.append(list1[i].left)
                if list1[i].right:
                    list2.append(list1[i].right)
            list.append(list3)
            list1 = list2
        return list