LeetCode101 对称二叉树

给定一个二叉树，检查它是否是镜像对称的。

 

先创建一个镜像的二叉树，即交换二叉树的左右子树，然后比较二叉树的异同即可。

注意判断异同的时候origin和new都可能单独为nullptr，不要漏掉情况

 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 isSymmetric(TreeNode* root) {
13         TreeNode* symmetricTree=build_symmetric(root);
14         return judge_same(root,symmetricTree);
15     }
16 
17     bool judge_same(TreeNode* origin, TreeNode* symmetric){
18         if(origin==nullptr)
19             return symmetric==nullptr;
20         if(symmetric==nullptr)
21             return false;
22         return origin->val==symmetric->val && judge_same(origin->left,symmetric->left)
23         && judge_same(origin->right,symmetric->right);
24     }
25 
26     TreeNode* build_symmetric(TreeNode* root){
27         if(root==nullptr)
28             return nullptr;
29         TreeNode* newTree=new TreeNode(root->val);
30         newTree->left=build_symmetric(root->right);
31         newTree->right=build_symmetric(root->left);
32         return newTree;
33     }
34 };

 

posted @ 2020-07-19 18:20  __rookie  阅读(142)  评论(0)  编辑  收藏  举报