在leetcode 如下题目中使用队列
637. 二叉树的层平均值：
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def averageOfLevels(self, root: Optional[TreeNode]) -> List[float]:
ans = []
queue = deque([root])
while queue:
sum = 0
cnt = len(queue)
for i in range(cnt):
node = queue.popleft()
sum += node.val
if node.left:
queue.append(node.left)
if node.right:
queue.append(node.right)
ans.append(sum/cnt)
return ans
标签：node,right,val,队列,self,queue,使用,python3,left From： https://www.cnblogs.com/jyfyonghu/p/18445574