226. Invert Binary Tree

/**
* 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:
TreeNode* invertTree(TreeNode* root) {
if(root==NULL)return root;
if(root->left==NULL&&root->right==NULL)return root;

TreeNode* r=root->right;
TreeNode* l=root->left;
root->right=invertTree(l);
root->left=invertTree(r);

return root;
}
};