/**

  * 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 swapLR(TreeNode* root){

         if(!root) return;

         else{

             TreeNode *t = root->left;

             root->left = root->right;

             root->right = t;

             swapLR(root->left);

             swapLR(root->right);

         }

     }

     TreeNode* invertTree(TreeNode* root) {

         swapLR(root);

         return root;

     }

 };