二叉树的镜像

操作给定的二叉树，将其变换为源二叉树的镜像。 

解：

public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;    public TreeNode(int val) {        this.val = val;    }}public class Solution {    public void Mirror(TreeNode root) {        if (root == null)            return ;        Mirror(root.left);        Mirror(root.right);        TreeNode temp = root.left;        root.left = root.right;        root.right = temp;    }}