Leetcode | 226. 翻转二叉树

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     TreeNode* invertTree(TreeNode* root) 
13     {
14         if(!root)
15             return nullptr;
16         dfs(root->left, root->right);
17         return root;
18     }
19     
20     void dfs(TreeNode* &p, TreeNode* &q)
21     {
22         if(!p && !q)
23             return;
24         std::swap(p, q);
25         if(p)   
26             dfs(p->left, p->right);
27         if(q)
28            dfs(q->left, q->right);     
29     }
30 };