class TreeNode:

def init(self, x):

self.val = x

self.left = None

self.right = None

@param root TreeNode类

@return int整型二维数组

class Solution: def levelOrder(self , root ): # write code here # 根节点为空时 if root is None: return [] res = [] pt = [root] #pr用来存放pt的下一层子节点 pr = [] #若pt为空列表时，结束 while len(pt) != 0: #a用来存放每一层结果 a = [] for i in pt: a.append(i.val) #若存在左子节点 if i.left is not None: pr.append(i.left) #若存在右子节点 if i.right is not None: pr.append(i.right) #pr传递给pr pt = pr #初始化pr为空列表 pr = [] res.append(a) return res