【LC刷题】DAY12：226 144 94 145

文章目录

【LC刷题】DAY12：226 144 94 145
- 226. 翻转二叉树 [link](https://leetcode.cn/problems/invert-binary-tree/)
- 101. 对称二叉树 [link](https://leetcode.cn/problems/invert-binary-tree/description/)
- 104. 二叉树的最大深度
- 559. N 叉树的最大深度 [link](https://leetcode.cn/problems/maximum-depth-of-n-ary-tree/description/)
- 111. 二叉树的最小深度 [link](https://leetcode.cn/problems/minimum-depth-of-binary-tree/description/)

226. 翻转二叉树 link

/*** 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) {if(!root){return root ;}swap(root->left, root->right);invertTree(root->left);invertTree(root->right);return root;}
};

101. 对称二叉树 link

/*** 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 == nullptr && right != nullptr) return false;else if (left != nullptr && right == nullptr) return false;else if (left == nullptr && right == nullptr) 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 false;}return compare(root->left, root->right);}
};

104. 二叉树的最大深度

/*** 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:int maxDepth(TreeNode* root) {if(!root){return 0;}queue<TreeNode*> q;q.push(root);int depth = 0;while(!q.empty()){int size = q.size();for(int i = 0; i< size; i ++){auto node = q.front();q.pop();if(node->left) q.push(node->left);if(node->right) q.push(node->right);}depth++;}return depth;}
};

559. N 叉树的最大深度 link

/*
// Definition for a Node.
class Node {
public:int val;vector<Node*> children;Node() {}Node(int _val) {val = _val;}Node(int _val, vector<Node*> _children) {val = _val;children = _children;}
};
*/class Solution {
public:int maxDepth(Node* root) {if(root==nullptr){return 0;}queue<Node*> q;q.push(root);int depth = 0;while(!q.empty()){int size = q.size();for(int i =0 ; i < size; i ++){auto node = q.front();q.pop();for(auto n : node->children ){q.push(n);}}depth++;}return  depth;}
};

111. 二叉树的最小深度 link

/*** 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:int minDepth(TreeNode* root) {if(!root){return 0;}queue<TreeNode*> q;q.push(root);int depth = 1;while(!q.empty()){int size = q.size();for(int i =0; i < size; i++){auto node = q.front();q.pop();if(node->left) q.push(node->left);if(node->right) q.push(node->right);if(!node->left && !node->right){return depth;}}depth++;}return depth;}
};