Leetcode 226. Invert Binary Tree(easy)

/* 求翻转二叉树，其实就是求二叉树的镜像


*/

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