leetcode之Binary Tree Zigzag Level Order Traversal

# 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 zigzagLevelOrder(self, root):
"""
:type root: TreeNode
:rtype: List[List[int]]
"""
if  not root:
return []
a = []
queue = [root]
b = 0
while queue:
if b == 0:
a.append([q.val for q in queue])
else:
a.append([q.val for q in queue][::-1])
queue = [q for node in queue for q in (node.left, node.right) if q]
if b == 0:
b = 1
else:
b = 0
return a