leetcode-easy-trees-102. Binary Tree Level Order Traversal-Y

# Definition for a binary tree node.
# 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]]
        """
        def deal(root,level):
            if not root:
                return 
            if len(self.res) <= level:
                self.res.append([root.val])
            else:
                self.res[level].append(root.val)
            deal(root.left,level+1)
            deal(root.right,level+1)
        self.res = []
        deal(root,0)
        return self.res