/**
 * 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) ;
        else 
        {
            swap(root->left,root->right);
            mirror(root->left),mirror(root->right);
        }

    }
};