invert-binary-tree

Invert Binary Tree

LeetCode #: 226

Difficulty: Easy

Topics: Tree.

Problem

Invert a binary tree.

Example:

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:

     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 f*** off.

Complexity Analysis

Time complexity: O(n).

Space complexity: O(h) where h is the height of the tree. O(n) in the worst case when h is equal to n.