Invert the Binary Tree

Given a binary tree A, invert the binary tree and return it.

Inverting refers to making left child as the right child and vice versa.

1 <= size of tree <= 100000

First and only argument is the head of the tree A.

Return the head of the inverted tree.

Input 1:

 
     1
   /   \
  2     3

Input 2:

 
     1
   /   \
  2     3
 / \   / \
4   5 6   7

Output 1:

 
     1
   /   \
  3     2

Output 2:

 
     1
   /   \
  3     2
 / \   / \
7   6 5   4

Explanation 1:

Tree has been inverted.

Explanation 2:

Tree has been inverted.