new_contents: class TreeNode(object):
      def __init__(self, x):
          self.val = x
          self.left = None
          self.right = None
  
  
  class Solution(object):
      def levelOrder(self, root):
          """
          :type root: TreeNode
          :rtype: List[List[int]]
          """
          queue = []
          res = []
          queue.append(root)
  
          if root is None:
              return res
  
          while len(queue) != 0:
              s_arr = []
              s = len(queue)
              for i in range(s):
                  node = queue.pop(0)
                  s_arr.append(node.val)
                  if node.left is not None:
                      queue.append(node.left)
                  if node.right is not None:
                      queue.append(node.right)
              res.append(s_arr)
          return res
  
subject: 完成了102题:Binary Tree Level Order Traversal