LeetCode 226. Invert Binary Tree （反转二叉树）

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution 
11 {
12     public TreeNode invertTree(TreeNode root) 
13     {
14         if(root == null)
15             return null;
16         
17         // continue children
18         invertTree(root.left);
19         invertTree(root.right);
20         
21         // swap left and right
22         TreeNode temp;
23         temp = root.left;
24         root.left = root.right;
25         root.right = temp;
26         
27         return root;
28     }
29 }