LeetCode Invert Binary Tree 反转二叉树

 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         if(!root)   return 0;//重要在这而已
14         if(root->left)    invertTree(root->left);
15         if(root->right)   invertTree(root->right);
16         TreeNode* tmp=root->right;
17         root->right=root->left;
18         root->left=tmp;
19         return root;
20     }
21 };