Leetcode: Invert Binary Tree

Question

Invert a binary tree.

4
/ \
2 7
/ \ / \
1 3 6 9
to
4
/ \
7 2
/ \ / \
9 6 3 1
Trivia:
This problem was inspired by this original tweet by Max Howell:
Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so fuck off.
Show Tags

Analysis

Solution

# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None

class Solution(object):
    def invertTree(self, root):
        """ :type root: TreeNode :rtype: TreeNode """
        return self.helper(root)

    def helper(self, root):
        if root==None:
            return None

        temp1 = self.helper(root.right)
        temp2 = self. helper(root.left)
        root.left = temp1
        root.right = temp2

        return root