/
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
/
class Solution {
public:
void mirror(TreeNode root) {
if(!root) return;

    TreeNode* tmp=root->left;
    root->left=root->right;
    root->right=tmp;

    mirror(root->left);
    mirror(root->right);
}

};