LeetCode 101. Symmetric Tree

Posted 2022-12-27 yy-1046741080

题目：判断一棵树的左子树和右子树是否对称。

 

解题思路：

1. 递归判断，对于每一棵非空树，如果左子树不与右子树对称，那么整棵树就不满足对称性。

 

 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     bool isSymmetric2(TreeNode* left,TreeNode* right)
13         if(left==NULL && right==NULL)
14             return true;
15         
16         else if(left==NULL || right==NULL)
17             return false;
18         
19         else if(left->val==right->val && isSymmetric2(left->left,right->right) && isSymmetric2(left->right,right->left))
20             return true;
21         
22         return false;
23     
24 
25     bool isSymmetric(TreeNode* root) 
26        if(root==NULL)
27            return true;
28         
29        return isSymmetric2(root->left,root->right);
30     
31 ;
32