102、Binary Tree Level Order Traversal

题目：

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

For example:

Given binary tree

{3,9,20,#,#,15,7}

,

3
/ \
9  20
/  \
15   7

return its level order traversal as:

[
[3],
[9,20],
[15,7]
]

解题思路：
二叉树的层次遍历

# 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 levtrav(q):
tmp = q[:]
for l in tmp:
x = q.pop(0)
if(x.left!=None):
q.append(x.left)
if(x.right!=None):
q.append(x.right)
return q

res,queue = [],[]
if(root):
res.append([root.val])
queue.append(root)
while(len(queue)!=0):
tmp = []
for l in queue:
if(l.left!=None):
tmp.append(l.left.val)
if(l.right!=None):
tmp.append(l.right.val)
if(tmp!=[]):
res.append(tmp)
queue = levtrav(queue[:])
return res