leetcode-101. 判断对称树 · Tree + 递归

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  */

 1 class Solution {
 2 public:
 3     bool isSymmetric(TreeNode* root) {
 4         if(root == nullptr)
 5             return true;
 6         else
 7             return Symmetric(root->left, root->right);
 8     }
 9     
10     bool Symmetric(TreeNode* left, TreeNode* right)
11     {
12         if(left == nullptr && right == nullptr)
13             return true;
14         else if (left == nullptr || right == nullptr)
15             return false;
16         if(left->val == right->val)
17             return Symmetric(left->left, right->right) && Symmetric(left->right, right->left);
18         else
19             return false;
20         
21         return true;
22     }
23 };