102-breadth-first-depth-二叉树的层序遍历.py

#
# @lc app=leetcode.cn id=102 lang=python3
#
# [102] 二叉树的层序遍历
#
from typing import Optional, List
from node import TreeNode


# @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 levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
        if not root:
            return []
        res = []
        q = [root]
        while len(q) != 0:
            n = len(q)
            level = []
            for _ in range(n):
                node = q.pop(0)
                level.append(node.val)
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
            res.append(level)
        return res


# @lc code=end