题目
Given the root of a binary tree, return the sum of values of its deepest leaves.
解题思路
按层进行BFS，如果下一层没有新的节点，返回当前层所有数的和
代码
class Solution:
def deepestLeavesSum(self, root: TreeNode) -> int:
q = [root]
while q:
tmp = []
for node in q:
if node.left:
tmp.append(node.left)
if node.right:
tmp.append(node.right)
if not tmp:
return sum([n.val for n in q])
q = tmp
