#107

Binary Tree Level Order Traversal II

pupil · 595 · lc medium +29 · verified · 67.7% accepted · 5,155 likes · top 74%

Description

Given the root of a binary tree, return a bottom-up collection of node values: starting from the deepest level and working up to the root, listing each level's values left to right.

Example 1:

Input: root = [3,9,20,null,null,15,7]

Output: [[15,7],[9,20],[3]]

Example 2:

Input: root = [1]

Output: [[1]]

Example 3:

Input: root = []

Output: []

Code

# 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 levelOrderBottom(self, root: Optional[TreeNode]) -> List[List[int]]:

# 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 levelOrderBottom(self, root: Optional[TreeNode]) -> List[List[int]]: