【LeetCode OJ】Binary Tree Level Order Traversal II
Problem Link:
https://oj.leetcode.com/problems/binary-tree-level-order-traversal-ii/
Use BFS from the tree root to traverse the tree level by level. The python code is as follows.
# Definition for a binary tree node
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None class Solution:
# @param root, a tree node
# @return a list of lists of integers
def levelOrderBottom(self, root):
"""
BFS from root, and record the values level by level
"""
# List of levels
res = []
# Special case: empty tree
if not root:
return res
level = [root]
while level:
temp = []
res.insert(0, [n.val for n in level])
for node in level:
if node.left:
temp.append(node.left)
if node.right:
temp.append(node.right)
level = temp
# Return
return res
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