No.135 - LeetCode226 - (经典)二叉树左右翻转

/**
 * 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 dfs(TreeNode* now){
        TreeNode* t = now->left;
        now->left = now->right;
        now->right = t;
        if(now->left!=NULL) dfs(now->left);
        if(now->right != NULL) dfs(now->right);
    }
    TreeNode* invertTree(TreeNode* root) {
        if(root == NULL) return NULL;
        dfs(root);
        return root;
    }
};