by Pawan Kumar @jsartisan
You are given the root of a binary tree. Transform the tree by flipping it horizontally (mirror image) and return its root.
To invert the tree, each node's left and right children should be swapped.
Constraints:
- 0 ≤ Number of nodes in the tree ≤ 100
- -100 ≤ Node value ≤ 100
Examples:
// Example 1:
// 1 1
// / \ / \
// 2 3 => 3 2
// / \ / \ / \ / \
// 4 5 6 7 7 6 5 4
const root1 = createTree([1, 2, 3, 4, 5, 6, 7]);
console.log(invertTree(root1));
// Output: [1, 3, 2, 7, 6, 5, 4]
// Example 2:
// 3 3
// / \ => / \
// 2 1 1 2
const root2 = createTree([3, 2, 1]);
console.log(invertTree(root2));
// Output: [3, 1, 2]
// Example 3:
const root3 = createTree([]);
console.log(invertTree(root3));
// Output: []
