【LeetCode OJ】Binary Tree Zigzag Level Order Traversal

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
# @param root, a tree node
# @return a list of lists of integers
def zigzagLevelOrder(self, root):
"""
BFS from the root.
For each level, insert a list of values into the result
"""
res = []
if not root:
return res
q = [root]
reverse = False
while q:
new_q = []
if reverse:
res.append([n.val for n in q][::-1])
else:
res.append([n.val for n in q])
reverse = not reverse
for node in q:
if node.left:
new_q.append(node.left)
if node.right:
new_q.append(node.right)
q = new_q
return res