Given the root of a binary tree, invert the tree and return its root.
Example 1
Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]
The number of nodes in the tree is in the range [0, 100].Swap left and right children, then recursively invert each subtree.
public TreeNode invertTree(TreeNode root) {
if (root == null) return null;
// Swap children
TreeNode tmp = root.left;
root.left = root.right;
root.right = tmp;
// Recurse
invertTree(root.left);
invertTree(root.right);
return root;
}Time: O(n) · Space: O(h) where h = tree height