淮安网站制作设计,外链屏蔽逐步解除,wordpress经常无响应,wordpress怎么显示翻页符号lletcode 230. 二叉搜索树中第K小的元素#xff0c;链接#xff1a;https://leetcode.cn/problems/kth-smallest-element-in-a-bst 题目描述 给定一个二叉搜索树的根节点 root #xff0c;和一个整数 k #xff0c;请你设计一个算法查找其中第 k 个最小元素#xff08;从 …lletcode 230. 二叉搜索树中第K小的元素链接https://leetcode.cn/problems/kth-smallest-element-in-a-bst 题目描述 给定一个二叉搜索树的根节点 root 和一个整数 k 请你设计一个算法查找其中第 k 个最小元素从 1 开始计数。 解法一 直接dfs中序遍历代码如下
/*** 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:vectorint res;int kthSmallest(TreeNode* root, int k) {dfs(root);return res[k - 1];}void dfs(TreeNode* root){if(!root)return;dfs(root-left);res.push_back(root-val);dfs(root-right);}
};解法二
/*** 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 kthSmallest(TreeNode* root, int k) {int res 0;if(root nullptr || k 1) {return -1;}int numOfLeftNodes getNumOfNodes(root-left);int numOfRightNodes getNumOfNodes(root-right);if (numOfLeftNodes k - 1) {return root-val;} else if (numOfLeftNodes k) {return kthSmallest(root-left, k);} else {return kthSmallest(root-right, k - numOfLeftNodes - 1);}}private:int getNumOfNodes(TreeNode* root) {if (!root) {return 0;}return getNumOfNodes(root-left) getNumOfNodes(root-right) 1;}
};
