Invert Binary Tree

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

Class TreeNode:
    val (int)
    left (TreeNode)
    right (TreeNode)

Input Format

First Parameter - TreeNode root

Output Format

Return the TreeNode.

Example 1:

Input: 
    4 2 7 1 3 6 9
Output: 
    4 7 2 9 6 3 1

Example 2:

Input:
    2 1 3
Output:
    2 3 1

Constraints:

• The number of nodes in the tree is in the range[1, 100].
• -100 <= Node.val <= 100
• Expected Time Complexity: O(n)
• Expected Space Complexity: O(n)