226 Invert Binary Tree

Problem Statement

Given the root of a binary tree, invert the tree, and return its root.

Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]


We are using a recursive approach so we have to first define a base case:
When the function gets passed a null pointer (meaning calling the function on a left or right branch of a node that has nothing there); you return the null pointer back.

Before we do our swap, we create a temp variable, swap and assign the temp to the swapped variable.

Then we make our recursive calls and in the end return the root.


var invertTree = function(root) {
  if (root === null) {
    return null;

  // Swap left and right subtrees
  let temp = root.left;
  root.left = root.right;
  root.right = temp;

  // Recursively invert left and right subtrees

  return root;


What is the Base case?

You are getting a null pointer for either left or right branch, then return null

How does inverting work?

Creating a temp variable, swapping, reassigning