【Invert Binary Tree】cpp

/**
 * 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 ) return root;
            TreeNode* tmp = root->left;
            root->left = Solution::invertTree(root->right);
            root->right = Solution::invertTree(tmp);
            return root;
    }
};