操作给定的二叉树，将其变换为源二叉树的镜像。 

输入描述:

二叉树的镜像定义：源二叉树     	    8    	   /  \    	  6   10    	 / \  / \    	5  7 9 11    	镜像二叉树    	    8    	   /  \    	  10   6    	 / \  / \    	11 9 7  5

1 /* 2 struct TreeNode { 3     int val; 4     struct TreeNode *left; 5     struct TreeNode *right; 6     TreeNode(int x) : 7             val(x), left(NULL), right(NULL) { 8     } 9 };*/10 class Solution {11 public:12     void Mirror(TreeNode *pRoot) {13         if(pRoot!=NULL){14             TreeNode *tmp=pRoot->left;15             pRoot->left=pRoot->right;16             pRoot->right=tmp;17             Mirror(pRoot->left);18             Mirror(pRoot->right);19         }20 21     }22 };