【代码随想录算法训练营第37期第十五天 | LeetCode226.翻转二叉树、101.对称二叉树 2】

代码随想录算法训练营第37期第十五天 | LeetCode226.翻转二叉树、101.对称二叉树 2

一、226.翻转二叉树

解题代码C++：

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode() : val(0), left(nullptr), right(nullptr) {}*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:TreeNode* invertTree(TreeNode* root) {queue<TreeNode*> que;if(root) que.push(root);while(!que.empty()){int size = que.size();for(int i = 0; i < size; i ++){TreeNode* node = que.front();que.pop();swap(node->left, node->right);if(node->left) que.push(node->left);if(node->right) que.push(node->right);}}return root;}
};

题目链接/文章讲解/视频讲解：
https://programmercarl.com/0226.%E7%BF%BB%E8%BD%AC%E4%BA%8C%E5%8F%89%E6%A0%91.html

二、101.对称二叉树 2

解题代码C++：

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode() : val(0), left(nullptr), right(nullptr) {}*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:bool compare(TreeNode* left, TreeNode* right){if(left == NULL && right != NULL) return false;else if(left != NULL && right == NULL) return false;else if(left == NULL && right == NULL) return true;else if(left->val != right->val) return false;else return compare(left->left, right->right) && compare(left->right, right->left);}bool isSymmetric(TreeNode* root) {if(!root) return true;return compare(root->left, root->right);}
};