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226.翻转二叉树.py
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226.翻转二叉树.py
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#
# @lc app=leetcode.cn id=226 lang=python3
#
# [226] 翻转二叉树
#
# @lc code=start
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
# Tips: tree, depth-first-search
class Solution:
def invertTree(self, root: TreeNode) -> TreeNode:
def dfs(node):
if not node:
return
left = dfs(node.left)
right = dfs(node.right)
node.left = right
node.right = left
return node
return dfs(root)
# Tips: tree, breadth-first-search
# class Solution:
# def invertTree(self, root: TreeNode) -> TreeNode:
# if not root:
# return
# queue = [root]
# while queue:
# node = queue.pop(0)
# # 每次都从队列中拿一个节点,并交换这个节点的左右子树
# node.left, node.right = node.right, node.left
# if node.left:
# queue.append(node.left)
# if node.right:
# queue.append(node.right)
# return root
# @lc code=end