104.二叉树的最大深度.py

#
# @lc app=leetcode.cn id=104 lang=python3
#
# [104] 二叉树的最大深度
#

# @lc code=start
# 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 maxDepth(self, root: Optional[TreeNode]) -> int:
        if root == None:
            return 0
        
        queue=[root]
        depth=0

        while queue:
            # 当前层的节点数
            n=len(queue)
            # 弹出当前层的所有节点，并将所有子节点入队列
            for _ in range(n):
                node=queue.pop(0)
                if node.left:
                    queue.append(node.left)
                if node.right:
                    queue.append(node.right)

            depth=depth+1

        return depth

# @lc code=end