# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
import queue
class Solution:
def findBottomLeftValue(self, root: TreeNode) -> int:
if not root:
return
q = queue.Queue()
q.put(root)
work = None #工作节点
while not q.empty():
count = q.qsize()
for _ in range(count):
work = q.get()
if work.right:
q.put(work.right)
if work.left:
q.put(work.left)
return work.val #最后一次访问的结点
