翻转二叉树

class Solution {public:    /**     * @param root: a TreeNode, the root of the binary tree     * @return: nothing     */     void look(TreeNode *root)     {         if(root==NULL)         return ;         if(root->left==NULL&&root->right==NULL)         return;         TreeNode *x;         x=new TreeNode;         x=root->left;         root->left=root->right;         root->right=x;         look(root->left);         look(root->right);     }    void invertBinaryTree(TreeNode *root) {        look(root);        // write your code here    }};