二叉树的镜像（剑指offer-18）

 1 /**
 2 public class TreeNode {
 3     int val = 0;
 4     TreeNode left = null;
 5     TreeNode right = null;
 6 
 7     public TreeNode(int val) {
 8         this.val = val;
 9 
10     }
11 
12 }
13 */
14 public class Solution {
15     public void Mirror(TreeNode root) {
16         if(root == null) return;
17         swap(root);
18         if(root.left!=null) Mirror(root.left);
19         if(root.right!=null)Mirror(root.right);
20     }
21     private void swap(TreeNode root){
22         TreeNode t = root.left;
23         root.left = root.right;
24         root.right = t;
25     }
26 }