leetcode - 230. 二叉搜索树中第K小的元素

题目

代码

#include <iostream>
#include <vector>
using namespace std;

typedef struct TreeNode{
    
	int val;
	struct TreeNode *left, *right;
}TreeNode, *BiTree;

void create(BiTree &root){
    
	int tn;
	cin>>tn;
	if(tn == -1){
    
		root = NULL;
		return;
	}
	root = new TreeNode;
	root->val = tn;
	create(root->left);
	create(root->right);
}

vector<int> nums;

void inorder(TreeNode *root){
    
	if(!root){
    
		return;
	}
	inorder(root->left);
	nums.push_back(root->val);
	inorder(root->right);
}

int kthSmallest(TreeNode* root, int k) {
    
	inorder(root);
	return nums[k-1];
}

int main(){
    
	int k, res;
	cin>>k;
	TreeNode* root;
	create(root);
	res = kthSmallest(root, k);
	cout<<res;
    return 0;
}