226. Invert Binary Tree

226. Invert Binary Tree

Invert a binary tree.

Example:

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:

     4
   /   \
  7     2
 / \   / \
9   6 3   1

My Solutions:

public class Solution {
    public TreeNode invertTree(TreeNode root) {
        if (root == null) {
            return root;
        }
        TreeNode left = root.left;
        TreeNode right = root.right;
        root.left = right; 
        root.right = left;
        invertTree(left);
        invertTree(right);
        return root;
    }
}