230. Kth Smallest Element in a BST Medium

1/**
2 * [230] Kth Smallest Element in a BST
3 *
4 * Given the root of a binary search tree, and an integer k, return the k^th smallest value (1-indexed) of all the values of the nodes in the tree.
5 *  
6 * Example 1:
7 * <img alt="" src="https://assets.leetcode.com/uploads/2021/01/28/kthtree1.jpg" style="width: 212px; height: 301px;" />
8 * Input: root = [3,1,4,null,2], k = 1
9 * Output: 1
10 * 
11 * Example 2:
12 * <img alt="" src="https://assets.leetcode.com/uploads/2021/01/28/kthtree2.jpg" style="width: 382px; height: 302px;" />
13 * Input: root = [5,3,6,2,4,null,null,1], k = 3
14 * Output: 3
15 * 
16 *  
17 * Constraints:
18 * 
19 * 	The number of nodes in the tree is n.
20 * 	1 <= k <= n <= 10^4
21 * 	0 <= Node.val <= 10^4
22 * 
23 *  
24 * Follow up: If the BST is modified often (i.e., we can do insert and delete operations) and you need to find the kth smallest frequently, how would you optimize?
25 * 
26 */
27pub struct Solution {}
28use crate::util::tree::{TreeNode, to_tree};
29
30// problem: https://leetcode.com/problems/kth-smallest-element-in-a-bst/
31// discuss: https://leetcode.com/problems/kth-smallest-element-in-a-bst/discuss/?currentPage=1&orderBy=most_votes&query=
32
33// submission codes start here
34
35// Definition for a binary tree node.
36// #[derive(Debug, PartialEq, Eq)]
37// pub struct TreeNode {
38//   pub val: i32,
39//   pub left: Option<Rc<RefCell<TreeNode>>>,
40//   pub right: Option<Rc<RefCell<TreeNode>>>,
41// }
42// 
43// impl TreeNode {
44//   #[inline]
45//   pub fn new(val: i32) -> Self {
46//     TreeNode {
47//       val,
48//       left: None,
49//       right: None
50//     }
51//   }
52// }
53use std::rc::Rc;
54use std::cell::RefCell;
55impl Solution {
56    pub fn kth_smallest(root: Option<Rc<RefCell<TreeNode>>>, k: i32) -> i32 {
57        0
58    }
59}
60
61// submission codes end
62
63#[cfg(test)]
64mod tests {
65    use super::*;
66
67    #[test]
68    fn test_230() {
69    }
70}
71