513. Find Bottom Left Tree Value刷题笔记

用队列解决

# 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 findBottomLeftValue(self, root: Optional[TreeNode]) -> int:
        queue = collections.deque([root])
        while queue:
            node = queue.popleft()
            res = node.val
            if node.right:
                queue.append(node.right)
            if node.left:
                queue.append(node.left)
        return res